RAMSEY CLARK HAS always been a bit of a maverick. A former attorney general and the son of a Supreme Court justice, he has eschewed the high-priced corporate practice that could have been his and instead has taken up the cause of the downtrodden.

Now Clark is saying that all lawyers should follow his example.

In a speech to the D.C. Bar Association, he hit Washington lawyers - who include some of the highest paid in the nation - square in their pocketbooks. Lawyers make too much money, he said. Instead of trying to make $150.000 a year or more, he said, they should devote at least one-third of their time taking cases for free "in the name of justice.

"I think we've got too many lawyers who value money more than justice," he said.

John H. Pickering, a partner in Wilmer, Cutler & Pickering, one of Washington's biggest and best known firms and who is president-elect of the D.C. Bar, acknowledged that Clark's speech - which he called "almost messianic in its delivery" - was troubling.

"He was trying to make the fat cats of the profession feel uncomfortable," said Pickering. "Certainly I feel uncomfortable over the fact there is a large unmet need for legal services."

He added that a lot of Washington lawyers - including members of his firm - practice "a lot" of public interest law, "and we're all uncomfortable that we can't do a lot more. But there are limits."

Clark practices what he preaches in a New York law firm he started with Melvin L. Wulf, a top attorney for the American Civil Liberties Union, and Alan H. Levine, a civil rights lawyer who has been active in the New York branch of the ACLU.

The firm is trying for a mix of clients. Those who can afford it will be charged the going rates, which average $100 an hour. Others will be given cut rates averaging $50 an hour. And those who can't afford any fees will be represented for free.

Figuring each lawyer will work 1,500 hours a year, the firm aims at billing one-third (500 hours) at full rates, one-third at cut rates and doing one-third for free. Clark said that should provide each lawyer with a net of $50,000 a year - far less than what partners in the top New York or Washington firms get but still "a pretty good" salary.

Clark said that no lawyer in the firm should make more than judges which would limit their income to about $50,000 a year. A federal district court judge is paid slightly more than that.

Clark's firm has had no trouble getting public interest cases - especially in fields of criminal law relating to the death penalty, parole procedures and search and seizure, and in the area of student and teacher rights. But he sees a "psychlogical problem" in attracting the paying customers.

"There is a psychological question as to whether commercial clients perceive lawyers known mostly for criminal justice and public interest cases as the kind of lawyers who can service their needs," Clark said.

"If lots of lawyers would limit their commerical practice to a level adequate to meet their needs and would extend public interest litigration, it would be the largest single resource to providing adequate legal services not only to the poor but to the middle class who have largely been priced out of the market," he said.

One of the most quoted sentences in President