[1] However, he established himself as a stage actor and director after moving to the United States in 1960, and became noted for directing plays featuring his wife in the 1970s beginning with A Better Place at Dublin's Gate Theatre (1973), then in America The Two of Us (1975), Saint Joan (1977–78), and a tour of California Suite (1976).

[2][3][4] The initial appearance led to a longer role, and he later went on to the variety version at the Victoria Palace in London's West End during the V-2 scare.

[7] Clark served for three years in the Merchant Navy (as an alternative to national service) as an indentured apprentice on the Silver Line ships Silverwalnut and Silvertarn.

Unknown in Canada, Clark became established as the original host of a weekly TV interview show Junior Magazine on the CBC's national network.

[10] He married Canadian actress Kay Hawtrey (who was six years his senior) in 1956 and appeared on stage in the musical Salad Days,[11] seasons of repertory in Toronto and Ottawa, and acted in television dramas.

[12] In 1966 he played a prison officer alongside Ray Milland in the Broadway production at the Music Box Theatre of Hostile Witness, under director Reginald Denham.

He divorced Hawtrey in 1967, and she returned to her native Toronto with their son, while Clark remained in New York City and studied method acting with Lee Strasberg, according to Cindy Adams.

[15] On 2 April 1967, Clark and Redgrave were married in Sidney Lumet's living room in New York City by an Ethical Culture minister.

[18] Clark produced and directed stage shows for Redgrave throughout the 1970s, including A Better Place at Dublin's Gate Theatre (1973) The Two of Us (1975), Saint Joan (1977–78, Broadway) and a tour of California Suite (1976).

In George Bernard Shaw's 15th-century set Saint Joan, under Clark's directorship, Redgrave portrayed the maid of Orleans opposite Tom Aldredge, Joseph Bova, and Philip Bosco.

He directed a 1981 episode of the CBS television series House Calls, in which Redgrave was then starring but she left under contentious circumstances and was replaced by Sharon Gless.

[23] Patti Hartigan of The Boston Globe described the play as a "triumph",[24] and Lloyd Rose of The Washington Post said of Redgrave's performance in Clark's production, "Particularly when she is not speaking, her face can seem to hold an impossible number of emotions simultaneously, yet such fullness of feeling is mysteriously unreadable.

Clark and Redgrave lived in Barnes, London and Howth, Dublin for a number of years before returning to the United States where he was a citizen.