Rabbit's tail is cutesy? Not entirely (4)
I believe the answer is:
scut
'rabbit's tail' is the definition.
(scut can mean a rabbit's tail)
'is cutesy? not entirely' is the wordplay.
'not entirely' indicates the answer is hidden within the clue.
'SCUT' is hidden in the letters of 'is cutesy'.
(Other definitions for scut that I've seen before include "Reindeer tail" , "Short tail of hare" , "Reindeer's tail" , "Short tail, such as rabbit's" , "Deer's tail" .)