What did you say in loo about French port? (2,5)
I believe the answer is:
le havre
'french port?' is the definition.
(port in France)
'what did you say in loo about' is the wordplay.
'what did you say' becomes 'eh' ('eh' is used to ask someone to repeat something).
'in' means one lot of letters goes inside another.
'loo' becomes 'lav' (lavatory).
'about' becomes 're' (regarding).
'eh' put inside 'lav' is 'lehav'.
'lehav'+'re'='LE HAVRE'
(Other definitions for le havre that I've seen before include "French Channel port" , "Northern French port" , "Port city of northern France" , "Port in Normandy" .)