Bird's complaint (6)
I believe the answer is:
grouse
I believe this is a double definition.
'bird's' is the first definition.
(grouse is a kind of bird)
'complaint' is the second definition.
(I've seen this before)
(Other definitions for grouse that I've seen before include "1D [GAMEBIRD] < having grumble" , "Complain pettily" , "Complain like game bird" , "Petty complaint" , "Complain like gamebird" .)