Go quickly in second vehicle (7)
I believe the answer is:
scamper
'go quickly' is the definition.
(I know that scamper is a more specific form of run)
'in second vehicle' is the wordplay.
'in second' becomes 's' (common abbreviation. I am not sure about the 'in' bit.).
'vehicle' becomes 'camper' (camper is a kind of vehicle).
's'+'camper'='SCAMPER'
Can you help me to learn more?
(Other definitions for scamper that I've seen before include "Run about briskly" , "Skip about briskly" , "Run and skip playfully about" , "Skip playfully with campers" , "Run quickly and lightly" .)