Rear deer (4)
I believe the answer is:
hind
I believe this clue is a double definition.
'rear' is the first definition.
('hind' can be a synonym of 'rear')
'deer' is the second definition.
(hind is a kind of deer)
(Other definitions for hind that I've seen before include "Rear - female deer" , "Rear - animal" , "posterior" , "Female beast" , "Female animal; at the back" .)