Sticking with jerk (3)
I believe the answer is:
tic
'jerk' is the definition.
(jerking movement by the body)
'sticking with' is the wordplay.
'with' indicates a hidden word.
'TIC' can be found hidden inside 'sticking'.
(Other definitions for tic that I've seen before include "Convulsion" , "Involuntary twitch" , "Involuntary muscular spasm" , "Muscle twitch" , "Nervous movement" .)