Serious enjoyment cycling by a French city (7)
I believe the answer is:
unfunny
'serious' is the definition.
(thesaurus)
'enjoyment cycling by a french city' is the wordplay.
I cannot really see how this works, but
'enjoyment' could be 'fun' (enjoyable activities) and 'fun' is present in the answer.
'city' could be 'ny' (short for New York) and 'ny' is located in the answer.
'a french' could be 'un' ('a' in French) and 'un' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for unfunny that I've seen is " Not amusing".)