A victory in French city, most gallant (7)
I believe the answer is:
bravest
'most gallant' is the definition.
('brave' can be similar in meaning to 'gallant')
'a victory in french city' is the wordplay.
'victory' becomes 'v'.
'in' means one lot of letters goes inside another.
'french city' becomes 'brest' (city in France).
'a'+'v'='av'
'av' inserted inside 'brest' is 'BRAVEST'.
(Other definitions for bravest that I've seen before include "Most valiant" , "Most courageous" , "Most valorous" , "Most daring" , "Most handsome" .)