Write about ancient city when calm (9)
I believe the answer is:
composure
'calm' is the definition.
('composure' can be a synonym of 'calm')
'write about ancient city' is the wordplay.
'write' becomes 'compose' ('compose' can be a synonym of 'write'**).
'about' indicates putting letters inside.
'ancient city' becomes 'ur'.
'compose' going around 'ur' is 'COMPOSURE'.
'when' acts as a link.
(Other definitions for composure that I've seen before include "Calm self-control" , "Coolness" , "Calm state" , "Calmness and self-control" , "tranquillity" .)