Bounced sound (4)
I believe the answer is:
echo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bounced sound</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for echo that I've seen before include "Noise heard again" , "Resound; (radar) return" , "Repeated sound" , "Reflection of sound - Greek nymph" , "Bounced sound" .)