Green’s Dictionary of Slang

(Aus.) a profit, a winning bet.

1966		J. Holledge Great Aust. Gamble 22: [A] lucky £10,000 collect on a winning Cups’ double.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 296: So the few punters who happened to back the successful protestor - which happened to start at a juicy quote of something like eights or tens - have a nice fat collect.