Dovecote sound (3)
I believe the answer is:
coo
'dovecote sound' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for coo that I've seen before include "Dove's call" , "Call like a dove" , "Sound like a dove" , "Murmur of a dove" , "Murmur, speak softly" .)