A metal (6)
I believe the answer is:
copper
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a metal</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that copper is a type of metal)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for copper that I've seen before include "old tub" , "Busy" , "Atomic number 29" , "Reddish-brown metallic element" , "One who nicks" .)