Roughly manoeuvred sail in French port (6)
I believe the answer is:
calais
'french port' is the definition.
(I've seen this before)
'roughly manoeuvred sail in' is the wordplay.
'roughly' becomes 'ca' (**).
'manoeuvred' indicates anagramming the letters.
'in' indicates putting letters inside.
'sail' is an anagram of 'lais'.
'ca' inserted inside 'lais' is 'CALAIS'.
(Other definitions for calais that I've seen before include "A ferry port in northern France" , "Mary Tudor said it would be found "lying in my heart"" , "Northern French port" , "French port opposite Dover" , "French port for ferry to England" .)