Cliff Robertson looks uncomfortable in a tuxedo.

The man who blew the lid off Hollywood's Begelman-Columbia Pictures affair, pulls off his black tie ("Do you mind?"), lights up a Carleton and crosses his shiny black evening shoes. The Robertsons - Cliff and his socialite/actress wife Dina Merrill - are relaxing in their 35th floor apartment. It is an elegant but cozy duplex overlooking the East River, with lots of plants, pillows and a bowl of fresh tulips next to a box of Nat Sherman gold-tipped cigarettes.

It's after midnight and the Robertsons have just returned from Liza Minnelli's birthday party last week, hosted by the designer, Halston. Robertson, 52, ruggedly handsome with thick black hair, a weathered tan and eyes the color of Aqua Velva, collapses in a chair, Merrill, 50, the former Nadenia Hutton Rumbough, daughter of the late Marjorie Merriweather Post, cereal heir and lifetime member of the Fashion Hall of Fame, smooths her golden hair and disappears into the kitchen. "It was her idea," Robertson stage-whispers. "I didn't want to go."

These days Cliff Robertson is speaking out. "If Watergate proved that the judicial system works, then this thing called Hollywoodgate is proving that the free press works . . . I'm going against big money. If they don't already have some sort of information on me, they're powerful enough to manufacture it," says the man who is talking candidly about what he calls "corruption" in tinsel town. He is talking on television shows, at parties and in the press and getting headlines like, "Cliff (PT 109) Robertson Is a New Profile in Courage." Cynics are saying it's the best role he's had in years.

"Black ladies in Bloomingdale's come up and congratulate me," he says. Merrill returns to the living room. "I'm proud of him," she says. "I think he's doing the right thing. People stop me on the street and say, 'Bravo for your husband.'"

Robertson says, yes, his life has changed since the day, almost a year ago, when he was told former Columbia president David Begelman had cashed a $10,000 check with Robertson's name on it. "It's on my mind now," the actor says, "all the time."

Begelman. Who misappropriated more than $60,000 of company funds and admitted forging Robertson's name on the check in question, resigned last month. The Los Angeles district attorney's office is investigating the matter, and Robertson says he will testify if Begelman is brought to trial.

Several attempts to contact Begelman last week were unsuccessful. His secretary said, "Mr. Begelman has no comment," and abruptly hung up.

It all started a year ago when Robertson, looking over papers for his 1976 tax return, came across an IRS 1099 from Columbia Pictures for $10,000. Since Robertson hadn't worked for the studio that year and hadn't received any money, he called and was told it was payment for promotional work. "I knew that couldn't be true," he says, "I've never been paid for any promotional work."

Meanwhile, his accountant discoverd that the check was forged. "The name on the back of the check was big black letter. 'Cliff Robertson.' I always sign my name 'Clifford P. Robertson Ill.'"

Robertson said he then got a phone call from Columbia president David Begelman, whom the actor remembers meeting years ago, although "I never really knew him."

Begelman told Robertson the check had been forged by a young man in the company. Begelman was willing to overlook the whole thing. Was Robertson "I told him yes, but that my accountant needed a copy of the check of tax purposes, so I wouldn't have to pay tax on it." He never heard from Begelman again.

Robertson and his accountant contacted the Wells Fargo bank in Beverly Hills and spoke to a teller who remembered the man who cashed the check. The teller said it was David Begelman. "When my accountant found out he told me. 'You know you're sitting on a hydrogen bomb. This can be dangerous to you personally and damaging to your career.' But it was a clear-cut case. I couldn't compromise the law." Robertson explains, "I couldn't live with myself." 'Cover-Up'

There has never been any love lost between Hollywood and Robertson, who describes the town as "jaded." Known as a maverick, he says, "Out there if you don't own a brown Mercedes, you're a failure."

After contacting the Beverly Hills police last summer, Robertson became frustrated by the lack of action which he later called "a cover-up." He went to the FBI, which - for his own safety - kept tabs on his whereabouts. Though he was never threatened, the actor recalls feeling "pretty concerned. A mixture of hopelessness and helplessness."

Meanwhile Columbia had completed its own probe - without interviewing Robertson. Begelman was suspended in October for nearly two months but in December - before the Securities and Exchange Commission had completed its investigation - he was reinstated.

"My wife and I sat in this very room," Robertson recalls, shaking his head. "We said to each other. 'Is this America? Is this really happening?'"

After contacting Morris Udall in Washington (Robertson's an old supporter), the actor went public with the story by calling The Washington Post, which after conducting its own investigation, published the story on Christmas Day.

"There's a small percentage of corrupt people in Hollywood. Only 1 per cent represent the pinnacle of power. They've been fightening people for years, and now they're frightening others into "ipso facto blacklisting' me."

"But now the offers are pouring in," interjects his wife, wearing a black chiffon Halston gown and spooning chocolate mousse from a champagne glass.

"No, honey, let's be honest now," Robertson says. "There were aperiod, up to about three weeks ago, when the phone stopped rining. I hear there's a very powerful person in Hollywood saying I'll never work again. It dosen't please me, but there's nothing I can do about it."

Frustrated by the lack of support from other hollywood figures, Robertson says Martin Ritt, the director, one of two other names on checks forged by Belgelman, is a friend of Belgelman and therefore was less inclined to blow the whistle.

"That's silly," says Ritt, himself a victim of blacklisting during the Mc Carthy era. "I didn't even know what was going on. I never got any tax from. The first I heard about it was through two lawyers from Columbia who asked me to verify the signature on the check. I told them it wasn't mine. My feeling is, let the courts take care of it. I'll testify. Personally, I think Robertson's being self-righteous and a little foolish. I don't think anybody gives a hoot about it out here."

Sue Mengers, an agent to the super stars, says Hollywood is going on with business as usual."My only comment on this "blacklisting" charge would be to check the record of Robertson's career in the past five years. How many major roles has he had in major studio productions?" Polished Oscar

Cliff Robertson once told an onterviewer, "I'm always the bridesmaid." His long career as a character actor ("I get bored playing the same type") has been a steady stream of supporting roles. His star - however bright - never rose to super status, hovering under Brando, Redford, Eastwood and McQeen.

"It's my own fault. I never promoted myself," says the actor who, while relatively unknown, was chosen by President John F. Kennedy to portray Kennedy's wartime exploits.

His mother died when Robertson was very young and he was raised by a grandmother and an adult, growing up comfortably in La Jolla, Calif.

Robertson's professional carer began on the stage in New York, where, after a stint in the World War II Merchant Marine, he had supported himself with a string of partime jobs - waiter, busboy, even a private detective. He then appeared in a few off Broadway plays and on Saturday morning television ("Rod Brown an the Rocket Rangers") before his film debut ("Picnic") in 1956.

His credits include "The Nakes and the Dead," "Gidget," "The Interns," "The Best Man" and "Charly" which won him the Academy Award for Best Actor in 1969.

The polished Oscar is displayed, along with silver trophies and mementos, on the top shelf of a bookcase in the living room. Tabletops and window sills are crowded with framed family photographs; Cliff and "Deenie" on their wedding day (1966); a younger, bearded Cliff on location; Cliff and his mother-in-laws; Dina, Cliff and the children. They have four between them. Would he like them to go into show business?

"No," Robertson declares, reaching for a half-empty tea cup. But his wife quickly interjects, "It would be up to them. If that's what they wanted."

Robertson lights another cigarette. "Oh, I don't know. Acting has been good to me. But if somebody told me tomorrow I couldn't do anything else, I wouldn't be satisfied." Beach Bum

In 1972, Cliff Robertson wrote, produced, directed and starred in "J. W. Coop," a rodco picture he calls his "most satisfying role." The film, a critical sucess, was not a box-office smach. The picture was released by Columbia."I'll tell you something else." Robertson sits up. "Columbia used money that ws supposed to promote "J. W. Coop' for another film - 'Lost Horizon.'" Is he bitter about such a routine business decision? "No, it happens all the time. I don't blame Columbia."

More recently, he starred in Brian de Palma's "Obsession" with Genevieve Bujold, "Three Days of the Condor," "Midway" and the television min-series, "Washington . . . Behind Closed Doors."

Which the week, he was scheduled to fly to Tahiti to start filming "Overboard." Another production, nearly completed.

The Robertsons like New York (Merrill's birthplace) and their phone is listed in the Manhattan directory. They own a house in La Jolla, where he learned to surf for his role in "Gidget."

"I think there's a little Gauguin a little of the beach bum in all of us, don't you? Who knows, I could always go back to being a beach bum." He laughs, unlit cigarette dangling from his mouth, mindful of the fact that he won't go down without a fight. The title of his autobiography, he laughs, will read: "White Hat/Empty Wallet."

My question is, "Where are all the superstars? We're talking about basic corruption in Hollywood. Where's Jane Fonda when we need her? If certain superstars - not just an actor like me - were bold enough to stand up and say, "We'veknown.' I want to see people stand up and speak up. Not just be emmbarrassed into it. This is just the tip of the iceberg."

Even so, Cliff Robertson says he likes to keep a low profile. In fact, he doesn't even have a pressagent. "These days" Merrill points out, "you don't need one."