Green’s Dictionary of Slang

to stub out a cigarette; to extinguish a cigarette leaving a still-smokeable stub.

1915		Liverpool Echo 19 July n.p.: I gave him [i.e. a soldier] a cigarette and he lighted it. But after he had taken three puffs his finger and thumb closed on the burning end, and he stuck the extinguished cigarette behind his ear. ‘You do not like my brand?’ I inquired. ‘Oh, yes sir, it's A.1. I'm only dimping - it's a trick we work in the trenches’.
1992		S. Armitage ‘True North’ in Kid 3: Spark up, then take turns / to dimp burning cigs through the diaphragm.