Block of cast metal (5)
I believe the answer is:
ingot
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">block of cast metal</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 ingot that I've seen before include "this must be cast" , "A lump of metal like gold" , "Metal casting" , "Mass of unwrought gold, for instance" , "expensive block" .)