Have (one's) end away British vulgar slang
To have sex
Did you have your end away last night?
The verb “have” should be conjugated according to its tense.
The phrase has been around since around 1910, according to the Shorter Slang Dictionary by Paul Beale and Eric Partridge. They say it's "usually of a man", and funnily enough there are recent examples online where it is used by females.