Unnatural high (8)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unnatural high</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for falsetto that I've seen before include "Artificial pitch" , "Artificially high voice pitch" , "Unnaturally high-pitched voice" , "Note production" , "Artificially high voice of latest sort" .)