US city showing elegance in the past (7)

I believe the answer is:

chicago

Here is my best explanation:

'us city' is the definition.
(I've seen this before)

'elegance in the past' is the wordplay.
'elegance' becomes 'chic' (chic is a kind of elegance).
'in the past' becomes 'ago' ('ago' can be a synonym of 'in the past').
'chic'+'ago'='CHICAGO'

'showing' is the link.

This clue was last seen in The Telegraph