Not loud (5)
I believe the answer is:
muted
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not loud</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 muted that I've seen before include "Viola is sometimes" , "Subdued; not bright" , "Not loud" , "Softened (of sound or colour)" , "Quietened" .)