Surprise or shock (4)
I believe the answer is:
jolt
This clue is a double definition.
'surprise' is the first definition.
(I've seen this in another clue)
'shock' is the second definition.
(I've seen this in another clue)
(Other definitions for jolt that I've seen before include "bump" , "Shock, jerk" , "Sudden shock" , "Sudden jerk" , "Sudden impact" .)