City with fashionable past (7)
I believe the answer is:
chicago
'city' is the definition.
(I know that Chicago is a city)
'with fashionable past' is the wordplay.
'with' says to put letters next to each other.
'fashionable' becomes 'chic' (chic means stylish or fashionable).
'past' becomes 'ago' (similar in meaning).
'chic' next to 'ago' is 'CHICAGO'.
(Other definitions for chicago that I've seen before include "Illinois port" , "Musical (in Illinois?)" , "3 city in the US" , "1970s' John Kander/Fred Ebb musical" , "America's Windy City" .)