Fools seen in the French mountain city (5)
I believe the answer is:
lhasa
'mountain city' is the definition.
'lhasa' can be an answer for 'city' (Lhasa is an example). I am unsure of the 'mountain' bit.
'fools seen in the french' is the wordplay.
'fools' becomes 'has' (I am not sure about this - if you are sure you should believe this answer much more).
'seen in' means one lot of letters goes inside another.
'the french' becomes 'la' ('the' in French).
'has' put inside 'la' is 'LHASA'.
Can you help me to learn more?
(Other definitions for lhasa that I've seen before include "Luxembourg's a" , "Sacred city" , "The Forbidden City in Tibet" , "Asian capital" , "Capital of Tibet" .)