Excessive cleaning (4,3,6)
I believe the answer is:
spit and polish
'excessive cleaning' is the definition.
(mocking term for excessive cleanliness)
This is the entire clue.
(Other definitions for spit and polish that I've seen before include "(Close attention to) military discipline" , "Punctilious military discipline" , "Careful procedures" , "Boots could profit from this" , "zealous neatness" .)