Police officer brought back tough duck (7)
I believe the answer is:
pochard
'duck' is the definition.
(I know that pochard is a type of duck)
'police officer brought back tough' is the wordplay.
'police officer' becomes 'cop' (cop is a kind of police officer).
'brought back' shows that the letters should be reversed in order.
'tough' becomes 'hard' (synonyms).
'cop' reversed gives 'poc'.
'poc'+'hard'='POCHARD'
(Other definitions for pochard that I've seen before include "Type of diving duck" , "Spanish wine" , "bird" , "diver" .)