Sound of a crow (3)
I believe the answer is:
caw
'sound of a crow' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for caw that I've seen before include "Rook's cry" , "Cry of a rook" , "Rook's call" , "Sound made by a crow, say" , "Call like rook" .)