Heavy metal bar (5)
I believe the answer is:
ingot
'heavy metal bar' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ingot that I've seen before include "A brick shaped lump of gold" , "Block (of steel, gold, etc)" , "Bar, often gold" , "Piece of precious metal" , "Unwrought metal cast in a mould" .)