A couple in the city (5)
I believe the answer is:
dijon
'city' is the definition.
(I have seen 'French city ' mean 'dijon' so perhaps 'city' could also mean 'dijon')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for dijon that I've seen before include "French city - type of mustard" , "French home of mustard?" , "French city associated with mustard" , "City of eastern France, known for mustard" , "Source of mustard" .)