Jumped in Sierra before accident (6)
I believe the answer is:
sprang
'jumped' is the definition.
(springing is a kind of jumping)
'sierra before accident' is the wordplay.
'sierra' becomes 's' (phonetic alphabet: alpha, bravo, charlie etc.).
'before' means one lot of letters go next to another.
'accident' becomes 'prang' (I've seen this before).
's'+'prang'='SPRANG'
'in' is the link.
(Other definitions for sprang that I've seen before include "Suddenly leapt (up)" , "Leaped forward" , "Bounded forward" , "suddenly developed" , "Jumped suddenly" .)