clean someone's clock

clean someone's clock

Beat, thrash, or defeat someone decisively, as in He's much bigger than you and could easily clean your clock. This term originated in the military. The use of clock is unclear but possibly alludes to hitting someone in the face (for "clockface"). [Slang; mid-1900s]
See also: clean, clock
References in periodicals archive ?
Basically, in but a few minutes and by merely swapping a few orifice plates, he or she could clean someone's clock and the control center would never catch on until someone physically inspected the orifice plate," said a former, long-time meter technician (who prefers anonymity for obvious reasons).