Stubborn creature (4)
I believe the answer is:
mule
'stubborn creature' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mule that I've seen before include "Backless slipper" , "Hybrid animal - slipper" , "Proverbially stubborn beast" , "on foot?" , "Obstinate quadruped" .)