Shocked the beginning came first! (8)
I believe the answer is:
startled
'shocked' is the definition.
(startling is a kind of shocking)
'the beginning came first' is the wordplay.
'the beginning' becomes 'start' (start is a kind of beginning).
'came first' becomes 'led' (I've seen this in other clues).
'start'+'led'='STARTLED'
(Other definitions for startled that I've seen before include "Frightened or suprised suddenly" , "Taken aback" , "Stunned, shocked" , "Taken by surprise" , "Surprised with fright" .)