Green’s Dictionary of Slang

to help in the commission of a swindle or fraud.

1828		G. Smeeton Doings in London 40: The billiard-marker refused to make any division of the spoil, or even to return the £10 which had been lost to him in bearing up the cull.
1873		Sl. Dict.
1894		Truth (Sydney) 26 Aug. 5/4: If the confidence business is to be done they [i.e. ‘magsmen’] ‘bear up’ to him [...] and ingratiate themselves into the good wishes of the visitor.