Run small van in which it is easy to crash? (7)
I believe the answer is:
scamper
'run' is the definition.
(scampering is a kind of running)
'small van in which it is easy to crash?' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'van in which it is easy to crash?' becomes 'camper' (you can sleep or 'crash' in a camper van).
's'+'camper'='SCAMPER'
(Other definitions for scamper that I've seen before include "Proceed hurriedly" , "Beetle" , "Skip about briskly" , "Skip around" , "Run with quick light steps" .)