March right up in front of a politician (5)
I believe the answer is:
tramp
'march' is the definition.
(tramping is a kind of marching)
'right up in front of a politician' is the wordplay.
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'in front of' means one lot of letters go next to another.
'politician' becomes 'MP' (Member of Parliament).
'rt' backwards is 'tr'.
'tr'+'a'+'mp'='TRAMP'
(Other definitions for tramp that I've seen before include "Down-and-out" , "Walk heavily - steamer" , "The man on the street?" , "Vagabond, hobo" , "Disreputable wanderer" .)