A European country's returned bird (4)
I believe the answer is:
skua
'bird' is the definition.
(skua is a kind of bird)
'a european country's returned' is the wordplay.
'european country's' becomes 'UK's' (United Kingdom).
'returned' shows that the letters should be reversed in order.
'a'+'uks'='auks'
'auks' in reverse letter order is 'SKUA'.
(Other definitions for skua that I've seen before include "Brownish sea bird" , "Large sea bird" , "One preying on gulls" , "Predatory northern seabird" , "Large predatory bird" .)