Clean your clock

Does anyone know the origination/true translations of the phrase:
"clean your clock"

'Clock' was certainly Cockney slang for 'face' when I was a boy. This may help give an explanation. More I don't know.

To clean someone's clock (for them) means to punch someone in the face. Clock is indeed London slang for face, though it is not as far as I know rhyming slang - and is simply derived from clocks also having faces. Why "to clean" should in this case mean to hit or strike is beyond me.