Make bright by rubbing (7)
I believe the answer is:
burnish
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">make bright by rubbing</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for burnish that I've seen before include "Buff up" , "Shine by rubbing" , "Rub to shiny finish" , "Polish to a high shine" , "Polish by rubbing" .)