Cuts loose from the tail! (4)
I believe the answer is:
scut
'the tail' is the definition.
(scut is a kind of tail)
'cuts loose' is the wordplay.
'loose' indicates anagramming the letters (letters are loosened from their original positions).
'cuts' anagrammed gives 'SCUT'.
'from' acts as a link.
(Other definitions for scut that I've seen before include "Short tail of hare" , "(Hare's) short upright tail" , "Reindeer tail" , "Small tail as of rabbit" , "Cuts into a small tail" .)