Very softly (10)
I believe the answer is:
pianissimo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">very softly</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for pianissimo that I've seen before include "(To be played) very quietly" , "Very quiet" , "Very quietly (music)" , "Very softly" , "Very soft (music)" .)