Tramping out with a game bird (9)
I believe the answer is:
ptarmigan
'game bird' is the definition.
(ptarmigan is a kind of game bird)
'tramping out with a' is the wordplay.
'out with' indicates anagramming the letters (out can mean wrong or inaccurate).
'tramping' mixed up with 'a' gives 'PTARMIGAN'.
(Other definitions for ptarmigan that I've seen before include "Type of mountain grouse" , "Bird of the grouse family" , "Grouse-like bird" , "turns white in winter" , "Highland game bird -- giant ramp (anag)" .)