Bad weather constraining a bird (8)
I believe the answer is:
wheatear
'bird' is the definition.
(wheatear is a kind of bird)
'bad weather constraining a' is the wordplay.
'bad' indicates an anagram.
'constraining' is an insertion indicator.
'weather' with letters rearranged gives 'wheater'.
'wheater' placed around 'a' is 'WHEATEAR'.
(Other definitions for wheatear that I've seen before include "Migrant's passion" , "Songbird" , "singer" , "bird" .)