Suburb of Paris, or part of Lyons (4)
I believe the answer is:
orly
'suburb of paris' is the definition.
The definition suggests a singular noun which matches the answer.
'part of lyons' is the wordplay.
'part' says to take the initial letters.
'lyons' becomes 'rly' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'of' is 'o'.
'o'+'rly'='ORLY'
'or' acts as a link.
Can you help me to learn more?
(Other definitions for orly that I've seen before include "French airport" , "Paris airport" , "Parisian airport" .)