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 quite understand how this works, but
'enjoyment' could be 'fun' (enjoyable activities) and 'fun' is found in the answer.
'city' could be 'ny' (short for New York) and 'ny' is found within the answer.
'a french' could be 'un' ('a' in French) and 'un' is found in the answer.
No letters remain.
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".)