Line is good in French capital (6)
I believe the answer is:
lisbon
'french capital' is the definition.
'lisbon' can be an answer for 'capital' (capital of Portugal). I am not sure about the 'french' bit.
'line is good' is the wordplay.
'line' becomes 'l' (used when specifying particular lines from a poem).
'good' becomes 'bon' (I've seen this in other clues).
'l'+'is'+'bon'='LISBON'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for lisbon that I've seen before include "Capital city on the Tagus" , "Portuguese capital" , "European capital" , "Capital of Portugal" , "Portugal's capital" .)