Young rabbit (6)
I believe the answer is:
kitten
This clue is a double definition.
'young' is the first definition.
(kitten is a kind of young)
'rabbit' is the second definition.
(I have seen 'Young rabbit ' mean 'kitten' so perhaps 'rabbit' could also mean 'kitten')
(Other definitions for kitten that I've seen before include "Baby cat" , "Young rabbit" , "Young of a beaver" , "found in litter" , "Little feline" .)