Vagrant with vehicle beginning to park (5)
I believe the answer is:
tramp
'vagrant' is the definition.
(I know that vagrant can be written as tramp)
'with vehicle beginning to park' is the wordplay.
'with' means one lot of letters go next to another.
'vehicle' becomes 'tram' (tram is a kind of vehicle).
'beginning to' indicates taking the first letters.
The first letter of 'park' is 'p'.
'tram' next to 'p' is 'TRAMP'.
(Other definitions for tramp that I've seen before include "Live as a vagrant" , "Heavily plod around" , "I might hitch a lift" , "Traveller" , "Trudge; vagrant" .)