Green’s Dictionary of Slang

offer n.

In phrases

on offer

liable to problems.

2000		J.J. Connolly Layer Cake 66: It’s like asking to get yourself choored, making yourself conspicuous, putting yourself on offer.
2007		N. ‘Razor’ Smith Raiders 2: The get-away driver was putting himself on offer for at least a seven-stretch if things went King Kong.