Begin to jump when surprised? (5)
I believe the answer is:
start
'begin' is the definition.
(synonyms)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for start that I've seen before include "Begin to recoil?" , "Take the first step" , "Jump suddenly" , "Beginning" , "Begin; flinch" .)