The French foreign port lacking interest (6)
I believe the answer is:
leaden
'lacking interest' is the definition.
(leaden can mean boring)
'the french foreign port' is the wordplay.
'the french' becomes 'le' ('the' in French).
'foreign port' becomes 'Aden' (port in Yemen).
'le'+'aden'='LEADEN'
(Other definitions for leaden that I've seen before include "Heavy and slow, as if weighted down with heavy metal" , "Leaned over in slow, heavy way" , "Heavy - overcast" , "Depressing - heavy" , "Heavy or slow, like dark-gray metal" .)