Clark Clifford knows things about this town and its power brokers that other people only think they know. The courtly 80-year-old Clifford was special counsel to President Harry S Truman and has advised Democratic presidents and would-be presidents for more than 40 years. It is often said that if he ever decided to write a book, publishers would be falling all over each other trying to buy it. It looks like Clifford is about to write that book.

Clifford, who also was secretary of defense under Lyndon Johnson, said yesterday that he has been thinking for quite a long time about writing a book about some "of the people I have been privileged to know." He said he has had a series of meetings with Random House in New York. "All I can say now," he added, "is I am interested; they are interested. We have agreed to have continuing discussions." Many major political figures over the years have turned to him for advice when they were in trouble, but there are those who doubt that Clifford, widely recognized as a consummate gentleman, would ever write the kind of tell-all book that would make splashy headlines.

Out and About

The conventional wisdom when retired House speaker Tip O'Neill signed a contract for his memoirs was that he would be too politic, too careful to write the stuff of a best seller. "Man of the House," written with William Novak and published by Random House, surprised a number of people with unexpectedly harsh characterizations of major political figures. The hardback went on to sell 525,000 copies; next week Random House will hold a paperback auction for the book that is expected to reach very high numbers ...

American composer John Cage escaped unharmed early yesterday as an arson fire destroyed much of the empty 1,400-seat Frankfurt Opera House. The 75-year-old Cage, in West Germany for the Sunday premiere of his opera "Europeras," was staying in an apartment in the building ...

Former White House chief of staff Donald Regan, who, with a little help from First Lady Nancy Reagan, resigned his job in the heat of the Iran-contra scandal, is now jumping into radio commentary. Regan, who had also been secretary of the treasury, has agreed to do weekday commentaries over the NBC Radio Network in a Washington-based series called "The Donald Regan Report." The 90-second spots, beginning Dec. 1, will feature Regan's views on politics, finance and the economy, among other subjects. Before joining the Reagan administration, the 68-year-old Regan was chairman and chief executive officer of Merrill Lynch & Co.

Ron Reagan substituted for his snowbound mother at pianist Vladimir Feltsman's Carnegie Hall debut Wednesday in an audience that also included ballet star Mikhail Baryshnikov and exiled Soviet poet Joseph Brodsky, who won this year's Nobel Prize for literature. The 35-year-old Soviet e'migre' was an immediate hit with the black-tie audience, which brought him back for two curtain calls before the intermission. Feltsman, complaining that he was denied artistic freedom, applied to Soviet authorities for an exit visa in 1979 and was then forbidden to play in public for two years ...

Sen. Richard Lugar (R-Ind.) broke a facial bone and suffered a cut over his eye yesterday when he slipped on the icy driveway at his home in McLean, spokesman Andy Fisher said. Lugar was treated at Bethesda Naval Hospital and released but will have to return Wednesday to have the facial bone set, according to Fisher.