Unfortunately no mains in large house (7)
I believe the answer is:
mansion
'large house' is the definition.
(I've seen this before)
'unfortunately no mains' is the wordplay.
'unfortunately' indicates an anagram (a bad or unfortunate spelling).
'no'+'mains'='nomains'
'nomains' with letters rearranged gives 'MANSION'.
'in' acts as a link.
(Other definitions for mansion that I've seen before include "Large dwelling" , "Big house" , "Large house" , "large residence" , "Opulent house" .)