Green’s Dictionary of Slang

spunkbone n.

[spunk n. (3) + bone n.1 (1a)]

the penis.

[UK]M. Manning Get Your Cock Out 84: She pulled his straining spunkbone from her mouth.

In compounds

spunkbone jockey (n.)

a male homosexual.

[UK]M. Manning Get Your Cock Out 87: He was going to find out what a Gibson Explorer felt like jammed up his pink fucking starfish arse, the spunkbone-jockey faggot.