Go northwards in French street for villain (5)
I believe the answer is:
rogue
'for villain' is the definition.
(rogue is a kind of villain)
'go northwards in french street' is the wordplay.
'northwards' says the letters should be written in reverse (in a down clue, letters go up or 'north').
'in' is an insertion indicator.
'french street' becomes 'rue' (French for street or road).
'go' backwards is 'og'.
'og' placed into 'rue' is 'ROGUE'.
(Other definitions for rogue that I've seen before include "Blackguard" , "Prankster" , "Scally" , "Dishonest chap; solitary (elephant)" , "A dishonest or unprincipled person" .)