Over in estate see game birds (5)
I believe the answer is:
geese
'birds' is the definition.
(goose is a kind of bird)
'over in estate see game' is the wordplay.
'over' says the letters should be written backwards.
'in' says the answer is hidden in the clue.
'eseeg' is hidden in the letters of 'estate see game'.
'eseeg' backwards is 'GEESE'.
(Other definitions for geese that I've seen before include "Sixth day of Christmas gift" , "Skein or gaggle?" , "Waterfowl" , "Domesticated birds" , "Stupid people" .)