Twitching (3)
I believe the answer is:
tic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">twitching</span>' is the definition.<br/ ><span class="explanation-format__explanation">(tic is a kind of twitching)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tic that I've seen before include "Nervous movement" , "Muscular contraction" , "Nervous response" , "Localised habitual twitch, especially to the face" , "Facial muscle spasm" .)