Facial spasm (3)
I believe the answer is:
tic
'facial spasm' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tic that I've seen before include "Jerky movement" , "Muscular contraction" , "Convulsive twitching" , "Twitch in anticipation" , "Convulsive twitch (of face)" .)