Green’s Dictionary of Slang

(Polari) to eat; thus to fellate (cite 2023 may be double entendre with play on fromage de tête, brawn, lit. ‘head-cheese’ and cheese n.¹ (2a) + head n. (2c)).

2019		P. Baker Fabulosa 293/2: jarry 1. to eat. 2. to fellate.
2023		R. Milward Man-Eating Typewriter 17: Christine Keeler jarries her last forkful of fromage de tête.