Buff; language (6)
I believe the answer is:
polish
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">buff</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that buff is a more specific form of buff)</span><br/ ><br/ >'<span class="explanation-format__original">language</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(Polish is a language)</span><br/ ><br/ ></span>
(Other definitions for polish that I've seen before include "Substance used to produce shine" , "Shine with soft cloth, say silverware" , "Give shine to" , "Europeans" , "taught in finishing school?" .)