Parking among the vehicles, walks (6)
I believe the answer is:
tramps
'walks' is the definition.
(tramp is a kind of walk)
'parking among the vehicles' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'among' is an insertion indicator (inserted letters are placed among others).
'the vehicles' becomes 'trams' (tram is a kind of vehicle).
'p' put inside 'trams' is 'TRAMPS'.
(Other definitions for tramps that I've seen before include "Walks heavily with vagrants" , "Vagrants or hoboes" , "Walks heavily like hobos" , "Walks heavily and firmly" , "Goes on a long walk" .)