First one to enter French city in film (8)
I believe the answer is:
earliest
'first' is the definition.
(I've seen this before)
'one to enter french city in film' is the wordplay.
'one' becomes 'i' (Roman numeral).
'to enter' indicates putting letters inside.
'french city' becomes 'arles' (I've seen this before**).
'in' indicates putting letters inside.
'film' becomes 'et'.
'i' inserted into 'arles' is 'arlies'.
'arlies' going within 'et' is 'EARLIEST'.
(Other definitions for earliest that I've seen before include "Soonest" , "Original or most previous" , "Next available" , "Ateliers (anag.)" , "First occurring" .)