Most pleasant street at the end of French city (6)
I believe the answer is:
nicest
'most pleasant' is the definition.
('nice' can be similar in meaning to 'pleasant')
'street at the end of french city' is the wordplay.
'street' becomes 'st'.
'at the end of' is a charade indicator (letters next to each other).
'french city' becomes 'nice'.
'st' after 'nice' is 'NICEST'.
(Other definitions for nicest that I've seen before include "Sin etc (anag)" , "Best" , "Insect (anag)" , "Most acceptable" , "most appetising" .)