Metal cast as a block (5)
I believe the answer is:
ingot
'metal cast as a block' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ingot that I've seen before include "Brick-shaped lump of cast metal" , "Piece of precious metal" , "A brick shaped lump of gold" , "A lump of metal like gold" , "Bar of bullion, for example" .)