Big house staff wrong about love (7)
I believe the answer is:
mansion
'big house' is the definition.
(I've seen this before)
'staff wrong about love' is the wordplay.
'staff' becomes 'man' (as in staffing or manning a particular place).
'wrong' becomes 'sin' (wrong can mean a sin or crime).
'about' is an insertion indicator.
'love' becomes 'o' (love means zero in tennis).
'sin' going around 'o' is 'sion'.
'man'+'sion'='MANSION'
(Other definitions for mansion that I've seen before include "Big house" , "Impressive house" , "Huge abode" , "Imposing house" , "Handsome house as for Lord Mayor" .)