Jumped up seconds before accident (6)
I believe the answer is:
sprang
'jumped up' is the definition.
(past tense of 'spring')
'seconds before accident' is the wordplay.
'seconds' becomes 's'.
'before' says to put letters next to each other.
'accident' becomes 'prang' (I've seen this before).
's'+'prang'='SPRANG'
(Other definitions for sprang that I've seen before include "bounced" , "freed prisoner" , "Leapt foward" , "Jumped or leaped in single movement (6(" , "suddenly developed" .)