Take a walk, parking vehicle first (5)
I believe the answer is:
tramp
'take a walk' is the definition.
(I've seen this before)
'parking vehicle first' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'vehicle' becomes 'tram' (tram is a kind of vehicle).
'first' means one lot of letters go next to another.
'p' put after 'tram' is 'TRAMP'.
(Other definitions for tramp that I've seen before include "A boat; a vagrant" , "Heavy footsteps" , "Merchant ship" , "cargo boat" , "Footslog" .)