Wild ass (6)
I believe the answer is:
onager
'wild ass' is the definition.
(I know that onager is a type of wild ass)
This is all the clue.
(Other definitions for onager that I've seen before include "wild beast" , "The ass is a strange orange" , "donkey" , "Asian wild ass - orange (anag)" , "Variety of wild ass found in central Asia" .)