Ancient city plot’s on ancient ground (14)
I believe the answer is:
constantinople
'ancient city' is the definition.
'constantinople' can be an answer for 'city' (Constantinople is an example). I also know that 'ancient' relates to this answer.
'plot's on ancient ground' is the wordplay.
'ground' indicates an anagram ('grind' the letters into a new form).
'plots'+'on'+'ancient'='plotsonancient'
'plotsonancient' is an anagram of 'CONSTANTINOPLE'.
(Other definitions for constantinople that I've seen before include "Istanbul formerly" , "Old city" , "capital no longer used" , "place that changed its name" , "Former name of Istanbul" .)