Architect horrible about large country home (9)
I believe the answer is:
nashville
'country home' is the definition.
(I've seen this before)
'architect horrible about large' is the wordplay.
'architect' becomes 'nash' (I've seen this before).
'horrible' becomes 'vile' (I've seen this before).
'about' indicates putting letters inside.
'large' becomes 'l'.
'vile' enclosing 'l' is 'ville'.
'nash'+'ville'='NASHVILLE'
(Other definitions for nashville that I've seen before include "Tennessee's capital" , "City in Tennessee" , "music centre" , "Centre of country and western" , "country town" .)