A low noise suggested by Ted (3)
I believe the answer is:
moo
'a low' is the definition.
(both can mean to make a cow noise)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for moo that I've seen before include "Bovine low" , "Guernsey noise?" , "Low (of cattle)" , "Farmyard sound" , "Cow's low" .)