Stridency (10)
I believe the answer is:
shrillness
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">stridency</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for shrillness that I've seen before include "Piercing quality (of sound)" , "Stridency" .)