Reflected sound (4)
I believe the answer is:
echo
'reflected sound' is the definition.
(an echo is a reflected sound)
This is the entire clue.
(Other definitions for echo that I've seen before include "Repeated sound" , "Be suggestive of" , "Before foxtrot" , "In Roman mythology, the nymph who loved Narcissus" , "Resound; (radar) return" .)