Ass (6)
I believe the answer is:
donkey
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ass</span>' is the definition.<br/ ><span class="explanation-format__explanation">(donkey is a kind of ass)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)