Jumped, causing small collision (6)
I believe the answer is:
sprang
'jumped' is the definition.
('spring' can be a synonym of 'jump')
'small collision' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'collision' becomes 'prang' (I've seen this before).
's'+'prang'='SPRANG'
'causing' acts as a link.
(Other definitions for sprang that I've seen before include "Jumped or leaped in single movement (6(" , "Jumped suddenly" , "Leapt foward" , "Bounded forward" , "released from prison" .)