Ermine in its summer coat (5)
I believe the answer is:
stoat
'ermine in its summer coat' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stoat that I've seen before include "Eating rabbit, he" , "Ermine in summertime?" , "Short-tail weasel" , "Source of ermine" , "Small carnivorous mammal of the weasel family" .)