Milne joey (3)
I believe the answer is:
roo
'milne joey' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for roo that I've seen before include "companion of Pooh" , "Kanga's son (Pooh)" , "Marsupial (informal)" , "Marsupial (abbrev.)" , "short jumper" .)