The prolific Ibrox skipper rifled in the winner in the 75th minute of a hard-fought encounter at Hampden Park to hand his Belgian boss his first trophy after just a few months at Ibrox.
The victory completed the clean sweep of domestic trophy wins for the full-back and it also meant Clement remains unbeaten in 14 games since taking over from Michael Beale in October.
It was the 28th time the Ibrox club have won the trophy – the first since 2011 – and they still have interest in the title and EL this season, with the Scottish Cup yet to start.
Both sides went into the game on a wet and windy Glasgow afternoon in fine fettle.
Rangers’ stunning 3-2 win away to Real Betis took them into the last 16 of the Europa League. Dons were already out of the Conference League, despite their clear 2-0 win over Eintracht Frankfurt.