Nail file material (5)
I believe the answer is:
emery
'nail file material' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for emery that I've seen before include "Rock used as abrasive" , "Coating on paper used as an abrasive" , "Abrasive powder" , "old comedian" , "Hard black-grey mineral used in grinding and polishing" .)