Green’s Dictionary of Slang

(Aus./N.Z.) a phr. meaning ‘be fair, give us a chance’.

1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 21: Cripes — fair crack of the whip — like no — but I’ll give it a burl.
1974		D. Ireland Burn 102: ‘Fair crack of the whip,’ McAllister says. ‘He’s talkin’ about past and present.’.
1988		McGill Dict. of Kiwi Sl.
2003		McGill Reed Dict. of N.Z. Sl. 75: fair crack of the whip/shake of the dice and fair suck of the saucestick/saveloy Appeals for fairness. ANZ.