Surprise reel (7)
I believe the answer is:
stagger
I believe this clue is a double definition.
'surprise' is the first definition.
(I've seen this before)
'reel' is the second definition.
(I know that reel can be written as stagger)
(Other definitions for stagger that I've seen before include "bowl over" , "Pitch" , "Reel - astound" , "Reel, walk unsteadily" , "Reel; amaze" .)