Green’s Dictionary of Slang

lies, a ruse, a subterfuge, a false charge.

1956		‘Charles Raven’ Und. Nights 98: Apart from the slur on his reputation of having fallen for a get-up by the Yard, Dusty wasn’t so down-hearted.
1970		G.F. Newman Sir, You Bastard 47: It could have been a get up.
1981		(con. c.1900) A. Harding in Samuel East End Und. 192: It was a summons for assaulting a policeman. I knew it was a get-up.
2007		N. ‘Razor’ Smith Raiders 135: He was living like a king on the proceeds of a get-up he was working.
2011		J.J. Connolly Viva La Madness 374: Ted was never dead. It was a get-up — he was being threatened.