Deaden (6)
I believe the answer is:
muffle
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deaden</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for muffle that I've seen before include "damp" , "Conceal" , "silence" , "Deaden(er of) sound" , "(Device to) reduce sound" .)