Extremely dirty and unpleasant house (7)
I believe the answer is:
dynasty
'house' is the definition.
(I know that house can be written as dynasty)
'extremely dirty and unpleasant' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'and' says to put letters next to each other.
'unpleasant' becomes 'nasty' (synonyms).
'dirty' with its middle taken out is 'dy'.
'dy'+'nasty'='DYNASTY'
(Other definitions for dynasty that I've seen before include "royal family" , "Ruling sequence" , "Sequence of hereditary rulers" , "Family line of rulers" , "Line of kings" .)