Alarmed RAN after beginning (8)
I believe the answer is:
startled
'alarmed' is the definition.
(I've seen this before)
'ran after beginning' is the wordplay.
'ran' becomes 'led' ('lead' can be a synonym of 'run').
'after' means one lot of letters go next to another.
'beginning' becomes 'start' (synonyms).
'led' after 'start' is 'STARTLED'.
(Other definitions for startled that I've seen before include "Frightened or surprised suddenly" , "Affrighted" , "Stunned, shocked" , "Shocked, alarmed" , "Frightened or suprised suddenly" .)