Moved suddenly – small accident (6)
I believe the answer is:
sprang
'moved suddenly' is the definition.
(I've seen this in another clue)
'small accident' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'accident' becomes 'prang' (I've seen this before).
's'+'prang'='SPRANG'
(Other definitions for sprang that I've seen before include "got out of jail" , "freed prisoner" , "Leaped forward" , "bounced" , "Suddenly leapt (up)" .)