Sticking with spasm (3)
I believe the answer is:
tic
'spasm' is the definition.
(I know that tic is a type of twitch)
'sticking with' is the wordplay.
'with' says the answer is hidden in the clue.
'TIC' is hidden within 'sticking'.
(Other definitions for tic that I've seen before include "Involuntary muscular spasm" , "Muscle twitch" , "Jerky movement" , "Minor muscle spasm" , "Convulsive spasm" .)