Polishing agent (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
emery
'polishing agent' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for emery that I've seen before include "Dick - - , late comedian" , "Rock used as abrasive" , "Hard, grey-black mineral used as 11 down" , "Hard grey-black mineral used as an abrasive" , "Abrasive powder" .)