Metal money (4)
I believe the answer is:
coin
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">metal money</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that coin is a type of metal money)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for coin that I've seen before include "stamp" , "Make up" , "Invent a word or phrase - for money?" , "Think up" , "American quarter, for example" .)