Smell masker (9)
I believe the answer is:
deodorant
'smell masker' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for deodorant that I've seen before include "hum suppressor" , "Antiperspirant" , "Smell masker" , "Substance that removes unwanted smells" , "Underarm protection?" .)