Sticking with twitch (3)
I believe the answer is:
tic
'twitch' is the definition.
(tic is a kind of twitch)
'sticking with' is the wordplay.
'with' indicates a hidden word.
'TIC' is hidden within 'sticking'.
(Other definitions for tic that I've seen before include "Convulsive twitch (of face)" , "Convulsion" , "Twitch in anticipation" , "Muscular contraction" , "Convulsive spasm" .)