Green’s Dictionary of Slang

a confrontation; violent or otherwise.

1948		S.L. Elliott Rusty Bugles 62: ‘By Jeez, they’ll have a ruddy jack-up here [...] if they don’t’.
1999		E. Bunker Mr Blue 254: I liked early morning jackups. The suckers often staggered to the door rubbing their glazed eyes.
2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Jack Up: Confrontational ‘request.’.