Wise person in a vehicle entering street (6)
I believe the answer is:
savant
'wise person' is the definition.
(I've seen this before)
'a vehicle entering street' is the wordplay.
'vehicle' becomes 'van' (van is a kind of vehicle).
'entering' is an insertion indicator.
'street' becomes 'st'.
'a'+'van'='avan'
'avan' put into 'st' is 'SAVANT'.
'in' is the link.
(Other definitions for savant that I've seen before include "Clever sort" , "Scholarly person" , "academic" , "Wise man" , "A learned or wise person from France" .)