The bird is returning to cover (6)
I believe the answer is:
siskin
'the bird' is the definition.
(siskin is a kind of bird)
'is returning to cover' is the wordplay.
'returning' says the letters should be written in reverse.
'to cover' becomes 'skin' (skin is a kind of cover).
'is' reversed gives 'si'.
'si'+'skin'='SISKIN'
(Other definitions for siskin that I've seen before include "Winger" , "Type of bird" , "Yellow-green finch" , "Greenish songbird of finch family" , "Yellowish-green finch" .)