Green’s Dictionary of Slang

a smart trick or clever dodge, esp. one that makes a task easier.

1899		C. Rook Hooligan Nights 63: Putting him up to about as many quiffs in crib-cracking as any boy ever got inside his napper.
1909		J. Ware Passing Eng. of the Victorian Era.
1925		N. Lucas Autobiog. of a Thief 72: Kid, I’ll give you one quiff [...] Never touch the dope, it’s hell.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 233: Quiff, A: Any xpecially ingenious, smart, tricky, or novel or improvised way of doing anything.