React to a shock (4)
I believe the answer is:
reel
'react to a shock' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for reel that I've seen before include "Turn around in the dance" , "Dance; winding cylinder" , "Totter" , "Move unsteadily (like a Scottish dancer?)" , "Stagger about in lively dance" .)