Left to Stu by a top Gunn.
Jack was thrilled his men battled back from a goal down and the loss of red-carded skipper David Niven.
The winner had been attributed to Stuart Leslie but Jack revealed: "It was Gunny who got the last touch."
It was 1-1 at half-time after Elgin defender Mark Nicolson's header floated in off the far post for an own goal then Pat Scullion's clearance bid cannoned in off Leslie for the leveller.
In 58 minutes Niven dragged back Sean Fitzharris and was shown a second yellow. But with nine minutes left Leslie challenged keeper Jamie Barclay to a high ball and Gunn nipped in to apply the final touch.
Clyde boss Jim Duffy said: "The game became scrappy - the winner typified that when our keeper didn't deal with a ball that looped up in the air."