Block for hammering (5)
I believe the answer is:
anvil
'block for hammering' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for anvil that I've seen before include "Verdi chorus from Il Trovatore" , "Block on which metals are hammered" , "hard block" , "part of the ear" , "Heavy metal block in forge" .)