Capital letter initially is good in France (6)
I believe the answer is:
lisbon
'capital' is the definition.
(capital of Portugal)
'letter initially is good in france' is the wordplay.
'initially' indicates taking the first letters.
'good in france' becomes 'bon' ('good' in French).
The first letter of 'letter' is 'l'.
'l'+'is'+'bon'='LISBON'
(Other definitions for lisbon that I've seen before include "Capital city and Treaty" , "Slob in Portuguese city" , "Portuguese capital" , "Capital city on the Tagus" , "European capital" .)