Bird to spoil metal container (6)
I believe the answer is:
martin
'bird' is the definition.
(martin is a kind of bird)
'spoil metal container' is the wordplay.
'spoil' becomes 'mar' (I've seen this before).
'metal container' becomes 'tin' (I've seen this before**).
'mar'+'tin'='MARTIN'
'to' is the link.
(Other definitions for martin that I've seen before include "Variety of swallow" , "Kind of swallow" , "Perhaps Dean" , "Man's name; bird" , "Dickens novel featuring Mr Pecksniff" .)