City redesigned as then (6)
I believe the answer is:
athens
'city' is the definition.
(Athens is a city)
'redesigned as then' is the wordplay.
'redesigned' is an anagram indicator.
'as'+'then'='asthen'
'asthen' anagrammed gives 'ATHENS'.
(Other definitions for athens that I've seen before include "Hasten (anag) -- capital city" , "European capital city" , "6 capital" , "City of the Parthenon" , "Capital of Greece" .)