Main problem with large conurbation (5)
I believe the answer is:
milan
'conurbation' is the definition.
The answer and definition can be both locations as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'main problem with large' is the wordplay.
'problem with' is an anagram indicator.
'large' becomes 'L' (eg in clothes sizes).
'main' mixed up with 'l' can make 'MILAN'.
Can you help me to learn more?
(Other definitions for milan that I've seen before include "Doorstep deliverer" , "Italian city with La Scala opera house" , "town" , "Northern Italian city" , "Capital of Lombardy" .)