Manspeak for
having sex with the wife.
Some men, especially those who have been married for years, don't perceive "walloping the donkey" as a pleasure. Instead, it is seen as an onerous, unpleasant and even
potentially dangerous chore. Something that needs to be done so that you can
get on with enjoying life's true pleasures (i.e. televised sport and beer) in comparative peace and quiet.