Ass (6)
I believe the answer is:
donkey
'ass' is the definition.
(I know that ass can be written as donkey)
This is the entire clue.
(Other definitions for donkey that I've seen before include "Ass; stupid person" , "Dunce" , "Animal for drudge work" , "-- Derby; -- jacket" , "Garment associated with building workers" .)