Sound from a ewe (3)
I believe the answer is:
baa
'sound from a ewe' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for baa that I've seen before include "Statement from those flocking" , "Sheep's bleat" , "Bleat of a sheep" , "Sound of a lamb" , "to Heathrow, the operators" .)