Opine about gripping head of game bird (6)
I believe the answer is:
pigeon
'bird' is the definition.
(pigeon is a kind of bird)
'opine about gripping head of game' is the wordplay.
'about' indicates anagramming the letters.
'gripping' is an insertion indicator.
'head of' says to take the initial letters.
The initial letter of 'game' is 'g'.
'opine' with letters rearranged gives 'pieon'.
'pieon' placed around 'g' is 'PIGEON'.
(Other definitions for pigeon that I've seen before include "run, perhaps" , "gull" , "Bird of towns and woods" , "Bird of the dove family" , "Common dove" .)