Old city rebuilt on ancient plots (14)
I believe the answer is:
constantinople
'old city' is the definition.
(I've seen this before)
'rebuilt on ancient plots' is the wordplay.
'rebuilt' indicates anagramming the letters.
'on'+'ancient'+'plots'='onancientplots'
'onancientplots' anagrammed gives 'CONSTANTINOPLE'.
(Other definitions for constantinople that I've seen before include "place that changed its name" , "Former name of Istanbul" , "Istanbul formerly" , "Old name of Istanbul" , "seat for emperor" .)