Piece of cast metal (5)
I believe the answer is:
ingot
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">piece of cast metal</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 ingot that I've seen before include "Piece of cast metal" , "Cast metal brick" , "expensive block" , "Mass of unwrought gold, for instance" , "Block of precious metal" .)