French port turned out with half of London (6)
I believe the answer is:
toulon
'french port' is the definition.
(I know that Toulon is a port)
'turned out with half of london' is the wordplay.
'turned' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'half of' means to take half the letters.
'london' halved is 'lon'.
'out' anagrammed gives 'tou'.
'tou'+'lon'='TOULON'
(Other definitions for toulon that I've seen before include "French city" , "French naval base" .)