Roman-style house (5)
I believe the answer is:
manor
'house' is the definition.
(manor house is a kind of house)
'roman-style' is the wordplay.
'style' indicates an anagram (style can mean to shape or design).
'roman' anagrammed gives 'MANOR'.
(Other definitions for manor that I've seen before include "police area" , "Large country house for Roman" , "patch" , "Land once belonging to a nobleman" , "Big house - police district" .)