Clair Johnson, 65, retired assistant editor of U.S. News and World Report, died Friday at his home in Washington of complications following a brain cancer operation.

He joined the magazine in 1954 as news-desk editor and from 1957 to 1969 was editor of the sport news section. Mr. Johnson then was associate executive editor, assistant executive editor until his retirement in 1977. Since then he had been editor and coowner with his wife, Leone P., of Ideas Unlimited, a publication for editors of company publications.

Mr. Johnson was born in Ashley, N.D. He attended the University of Oregon. He worked as a reporter for his hometown weekly, and later was managing editor of the Macon, Ga., Daily Telegraph. During World War II, he covered Congress for the Washington bureau of the Associated Press.

From 1946 to 1949, Mr. Johnson was executive news editor of the Salt Lake Tribune. He then joined Congressional Quarterly News Features as managing editor.

A member for many years of the National Press Club, he was editor of the Npc Record. He was an active member of Sigma Delta Chi journalism society.

In addition to his wife, of Washington, he is survived by a son, Alan Clair, of Santa Ana, Calif.; a daughter, Carolyn Anne, of Alexandria, and a sister, Mary Earle Iverson, of Cass Lake, Minn.