Extremely dingy and unpleasant house (7)
I believe the answer is:
dynasty
'house' is the definition.
(I've seen this before)
'extremely dingy and unpleasant' is the wordplay.
'extremely' suggests removing the centre.
'and' means one lot of letters go next to another.
'unpleasant' becomes 'nasty' ('nasty' is associated in meaning with 'unpleasant'**).
'dingy' with its centre removed is 'dy'.
'dy'+'nasty'='DYNASTY'
(Other definitions for dynasty that I've seen before include "Series of hereditary rulers" , "rule" , "Sequence of hereditary rulers" , "Family line of rulers" , "Line of hereditary rulers" .)