TOM C. CLARK was one of the rare associate justices of the Supreme Court whose stature continued to grow after he "retired." He left the Court a decade ago to avoid any possible appearance of conflict of interest after his son, Ramsey, was named Attorney General. But he never really retired. He continued to make his judical services available, on spot duty, around the country, helping out other judges who were overworked. And he gave endlessly of his time to organizations and groups working to improve tha administration of justices. In the process, he gained new friends and admirers almost everywhere.

Tom Clark came to Washington from Texas 40 years ago as a lawyer in the Department of Justice. He became the assistant attorney general during World War II, Attorney General in 1945 and a member of the Supreme Court in 1949. But he never seemed far removed from Texas. He liked to conceal in keen mind behind the drawl and words of a poor country boy, and he always had time to be friendly with anyone who wanted a few words with him.

His record during 18 years on the Court was marked far more by pragmatism than by theory. His opinions, particularly in the early years, were often criticized - vigorously so by this newspaper - for displaying the attitudes of a prosecutor more often than the attitudes of a judge. But he cast the crucial vote, and wrote the Court's opinion, in a 1961 case expanding the exclusionary rule to cover criminal trials in state courts over the violent objections of most prosecutors and police officials. And he wrote the Court's opinion in 1963 when it held unconstitutional the use of prayer and Bible reading as devotional exercises in the public schools.

But Tom Clark's greatest contributions were off the bench. He fought for better judges - state as well as federal. He urged them, once they were judges, to go back to school to learn the art of their new jobs. He worked for more efficient courts and for ways to ease the burdens of citizens who became enmeshed in them. He wanted the substance of justice, not just the form of it, to be available to all citizens wherever they happened to live. And he spend what would be normally considered the golden years of retirement trying to advance that worthy cause.