Repeating sound effect (4)
I believe the answer is:
echo
'repeating sound effect' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for echo that I've seen before include "Let's hear it again for the Greek nymph who loved Narcissus in vain" , "Reiterate" , "Sound following" , "A natural sound reflection" , "Reverberation of sound" .)