Green’s Dictionary of Slang

1. (US prison) of a problem, dealt with, usu. after a fight.

2000

Other Side of the Wall: Prisoner’s Dict. July 🌐 Stiched up: A problem that has been taken care of, generally through a fight.

2. of a person, in one’s power.

2000		J.J. Connolly Layer Cake 134: Don’t worry about this guy, we’ve got him well stitched up.
2007		S. Maloney Sucked In 211: If the central panel wasn’t stitched up so tight, we’d actually have a real chance.