Public transport parking in March (5)
I believe the answer is:
tramp
'march' is the definition.
(tramping is a kind of marching)
'public transport parking' is the wordplay.
'public transport' becomes 'tram' (I've seen this in another clue).
'parking' becomes 'p' (abbreviation on road signs).
'tram'+'p'='TRAMP'
'in' is the link.
(Other definitions for tramp that I've seen before include "Heavy footsteps" , "Footslog" , "Vagrant, drifter" , "Lady or gentleman of the road or roving ship" , "Vagrant, hobo" .)