clean (someone's) clock
To thoroughly trounce, defeat, or beat up someone. Watch it, pal, or I'll clean your clock for you! The visitors really cleaned the home team's clock tonight!
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]
clean someone's clock
1 give someone a beating. 2 defeat or surpass someone decisively. North American informal Clock is used here in the slang sense of ‘face’.
clean (someone's) clock
Slang To beat or defeat decisively: "Immense linemen declared their intentions to clean the clocks of opposing players" (Russell Baker).