Nail smoother (5)
I believe the answer is:
emery
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nail smoother</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for emery that I've seen before include "Abrasive powder" , "Hard grey-black mineral used as an abrasive" , "hard stuff" , "Abrasive material" , "Coating on paper used as an abrasive" .)