 He was a law clerk to Justice Byron White at the Supreme Court during the October term, 1966 and practiced law at Wilmer, Cutler & Pickering, in Washington, D.C. and London from 1967 to 1990.Clevenger was nominated by President George H. W. Bush to the United States Court of Appeals for the Federal Circuit, to the seat vacated by Judge Oscar Hirsh Davis, on January 24, 1990.He was confirmed on April 27, 1990, received his commission on April 30, 1990 and assumed duties on May 3, 1990.