Posh daily in top class city (9)
I believe the answer is:
bucharest
'city' is the definition.
(Bucharest is an example)
'posh daily in top class' is the wordplay.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'daily' becomes 'char' (both can mean a cleaner).
'in' indicates putting letters inside.
'top class' becomes 'best' (the very best).
'u'+'char'='uchar'
'uchar' put into 'best' is 'BUCHAREST'.
(Other definitions for bucharest that I've seen before include "Capital of Romania" , "Balkan city" , "Romanian capital" , "European capital" , "European city" .)