Architect by awful housing left country’s main city (9)
I believe the answer is:
nashville
'city' is the definition.
(I know that Nashville is or was a state capital)
'architect by awful housing left' is the wordplay.
'architect' becomes 'nash' (I've seen this before).
'by awful housing left' becomes 'ville' (I am not sure about this - if you are sure you should believe this answer much more).
'nash'+'ville'='NASHVILLE'
'country's main' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for nashville that I've seen before include "Grand Ole Opry city" , "US city" , "country town" , "Where the Grand Ole Opry comes from" , "Centre of country and western" .)