A dental cleaner (10)
I believe the answer is:
toothpaste
'a dental cleaner' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for toothpaste that I've seen before include "Dentifrice" , "Dental cleaner" , "Cleaning item required" , "Cleaner used in bathroom" , "Substance with a fresh flavour" .)