Green’s Dictionary of Slang

1. one who participates in corruption .

1894

Truth (Sydney) 6 May. 3/8: I hope you enjoyed the turkey and ham I sent you for the ‘ready-up’ as instructed by you through Warder — [...] He had ‘turkey and ham,’ ‘ducks and asparagus and other luxuries’ all for being a ‘ready-up’.

2. (Aus.) a conspiracy or swindle; a fake.

1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 127: READY-UP slang to suborn evidence [...] to plant goods to tempt a thief: to give opportunity for crime then detect the criminal, would be a ready up.
1902		Sydney Sportsman (Surry Hills, NSW) 5 Mar. 1/1: The Fourteen-one Handicap at Forest Lodge was no doubt a ‘ready up’' for the books to fall in.
1926		J. Doone Timely Tips For New Australians 21: READY-UP.—A conspiracy.
1943		‘Myles na gCopaleen’ Faustus Kelly in ‘Flann O’Brien’ Stories & Plays (1973) 167: He’s down to smell out the ready-up about the rate collector or my name isn’t Reilly.
1955		N. Pulliam I Travelled a Lonely Land (1957) 238/1: ready-up – a hoax or trap.