> this is common enough idiom here in the colonies, meaning to beat or defeat decisively... I've no idea how or when it
originated -- as a guess, it could be just a combining of two related colloquial usages: to clean up on and to clock (the
latter seems to be Irish slang).

Oh, yes. To 'clock' means to hit or punch derived, I suppose, from the sound of knuckle against jaw combined with the rattle of teeth, but it is widely used in Britain too and I think it originated there. I'll go with that combination theory.