Metal alloy (5)
I believe the answer is:
brass
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">metal alloy</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for brass that I've seen before include "some musicians!" , "It's there, if muck's there" , "impudence" , "Money - cheek!" , "Impertinence" .)