Game bird losing height — was one entitled to land? (7)
I believe the answer is:
peasant
'one entitled to land?' is the definition.
(peasants worked on land)
'game bird losing height' is the wordplay.
'game bird' becomes 'pheasant' (pheasant is a kind of game bird).
'losing' indicates named letters should be taken away.
'height' becomes 'h' (abbreviation in geometry).
'pheasant' with 'h' removed is 'PEASANT'.
'was' acts as a link.
(Other definitions for peasant that I've seen before include "Rural person of low class" , "Provincial" , "rude fellow" , "Lowly tiller of land" , "Country labourer" .)