Coat of a cat (3)
I believe the answer is:
fur
'coat of a cat' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fur that I've seen before include "Animal-skin coat" , "Deposit inside kettles" , "Eg, sable or ermine" , "Coating formed on sick person's tongue (3)" , "Coating formed on tongue of sick person" .)