Something to excite a fan of necking bad French port (5-4)

'port' is the definition.
(Saint-Malo is a port in France)

'something to excite a fan of necking bad french' is the wordplay.
'something to excite' becomes 'SA' (abbreviation for sex appeal).
'a fan of' becomes 'into' (being into something means being a fan of it).
'necking' is an insertion indicator (neck can mean to swallow).
'bad french' becomes 'mal' (I've seen this in other clues).
'into' enclosing 'mal' is 'intmalo'.
'sa'+'intmalo'='SAINT-MALO'