Polish enthusiast (4)
I believe the answer is:
buff
I believe this clue is a double definition.
'polish' is the first definition.
(buffing is a kind of polishing)
'enthusiast' is the second definition.
(I've seen this in another clue)
(Other definitions for buff that I've seen before include "Blow" , "Bare skin - enthusiast" , "excellent muscle tone" , "light shade" , "Polish; expert, devotee" .)