Gritty powder (5)
I believe the answer is:
emery
'gritty powder' 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 "Hard grey-black mineral used as an abrasive" , "old comedian" , "Hard, grey-black mineral used as 11 down" , "Abrasive powder" , "Abrasive material" .)