A fan of Scottish First Division side Clyde, Clark came out of retirement in 1983 to help Clyde when they had a goalkeeping injury crisis. His father, Tom, was once the chairman of Clyde. In autumn 1984 he once more came out of retirement to keep goal for Forres Mechanics in a 1–0 victory over Buckie Thistle in the Highland League Cup Final held at Elgin.
Clark set the British top-flight record for not conceding a goal during league games (at 1,155 minutes) in the 1970–71 season, until Edwin van der Sar set a new mark on 8 February 2009. He also briefly held the world record, until Bulgarian goalkeeper Stoyan Yordanov set a new record of 1202 minutes in May 1971.Fraser Forster broke the Scottish league record in 2014 and was congratulated by Clark after the match in which it was surpassed.
His son Jamie has played in Major League Soccer and is currently Head Soccer Coach at University of Washington. His son Tommy, a paediatrician, is the founder and executive director of the HIV prevention organisation Grassroot Soccer. His daughter, Jennifer Clark, is also a soccer coach.