Sound reverberation (4)
I believe the answer is:
echo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sound reverberation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for echo that I've seen before include "Ape" , "Reflect sound" , "E; reverberation" , "repetitive" , "Repetition of sound" .)