Green’s Dictionary of Slang

kwef n.

also kweff

(UK black, gang) a n act of violence, thus as v. to kill by stabbing or shotting; to attack.

[UK]T. Thorne (ed.) ‘Drill Slang Glossary’ at Forensic Linguistic Databank 🌐 Kwef - violence Kweff, Queff – kill with gun or knife, harm, attack.