Son is not with mother, left close to bordello in walled city (5-4)

'walled city' is the definition.
(city in France)

'son is not with mother left close to bordello' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'is not with' becomes 'aint' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mother' becomes 'ma' (Ma is another word for mother or mum).
'left' becomes 'l' (common abbreviation).
'close to' indicates one should take the final letters (the close/ending of).
The last letter of 'bordello' is 'o'.
's'+'aint'+'ma'+'l'+'o'='SAINT-MALO'

'in' is the link.

Can you help me to learn more?