Italian-born Diego Cogolato, 29, admitted manslaughter on the grounds of diminished responsibility and was jailed for six years by Mr Justice Douglas Brown.
The court heard that Cogolato suffered a "transient psychotic episode", while repeatedly stabbing Mr Clark, 54, at his home. Passing sentence, the judge said: "You killed your friend in a frenzied attack, while you were in a psychotic state which may have been brought on by a combination of drugs, both prescribed and illicit."
Ossie Clark, the eccentric designer who was adored in the swinging Sixties by the likes of Mick and Bianca Jagger, Yoko Ono, and Jimi Hendrix, was found stabbed to death in his council flat in London on 7 August last year.
Widely regarded as a brilliant craftsman he became an icon of his age and his clothes were described as "sex incarnate".
He won a place at Manchester School of Art, where he was classmate with David Hockney, took up fashion design and went on to the Royal College of Art in 1961.
Seven years later, he married textile designer Celia Birtwell. The couple, who later divorced, had two sons.
But his golden era ended in 1974 and by the early 1980s he was bankrupt, reduced to sleeping on friends' sofas.