Sticking with jerk (3)
I believe the answer is:
tic
'jerk' is the definition.
(I've seen this before)
'sticking with' is the wordplay.
'with' indicates the answer is hidden within the clue.
'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" .)