Murmur sweetly “Blimey!” (3)
I believe the answer is:
coo
'murmur' is the definition.
(cooing is a kind of murmuring)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for coo that I've seen before include "Breathe" , "Murmur of a dove" , "Pigeon's sound" , "Pigeon call" , "Murmur amorously" .)