Iron block in Roman villa (5)
I believe the answer is:
anvil
'iron block' is the definition.
(I've seen this before)
'in roman villa' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ANVIL' can be found hidden inside 'roman villa'.
(Other definitions for anvil that I've seen before include "Alvin (anag.)" , "hard block" , "Smithy's block" , "Block used in forge" , "Forging equipment" .)