Surprise, take aback (7)
I believe the answer is:
startle
This clue is a double definition.
'surprise' is the first definition.
(to startle someone is to surprise or shock them)
'take aback' is the second definition.
(startling is a kind of taking aback)
(Other definitions for startle that I've seen before include "Make jump" , "Astonish" , "Cause to jump" , "Cause shock/alarm" , "Take (someone) aback" .)