Information on old American city (5)
I believe the answer is:
genoa
'city' is the definition.
(Genoa is an example)
'information on old american' is the wordplay.
'information' becomes 'gen' (gen can informally mean information).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'old' becomes 'o' (abbreviation).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'gen'+'o'+'a'='GENOA'
(Other definitions for genoa that I've seen before include "North Italian port" , "Italian city has no age, oddly" , "City of Italy" , "Type of rich fruit cake" , "NW Italian sea port" .)