Portion's free, served with good English game bird (9)
I believe the answer is:
partridge
'game bird' is the definition.
(partridge is a kind of game bird)
'portion's free served with good english' is the wordplay.
I cannot really see how this works, but
'free' could be 'rid' ('rid' can be a synonym of 'free') and 'rid' is located in the answer.
'good' could be 'g' (abbreviation) and 'g' is found within the answer.
'english' could be 'e' (abbreviation) and 'e' is located in the answer.
'portion' could be 'part' ('part' can be a synonym of 'portion') and 'part' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for partridge that I've seen before include "Flier" , "Flighty type" , "sort of quail" , "Peculiarly apt girder for the game bird" , "Game bird (in a pear tree?)" .)