Imposing residence for chap is no ruin (7)
I believe the answer is:
mansion
'imposing residence' is the definition.
(I've seen this before)
'chap is no ruin' is the wordplay.
'chap' becomes 'man' (chap can mean a man).
'ruin' indicates an anagram.
'is'+'no'='isno'
'isno' is an anagram of 'sion'.
'man'+'sion'='MANSION'
'for' acts as a link.
(Other definitions for mansion that I've seen before include "Grand house" , "Stately home" , "Handsome house as for Lord Mayor" , "Huge abode" , "Large building" .)