Extremely dreary and unpleasant line (7)
I believe the answer is:
dynasty
'line' is the definition.
(I know that dynasty is a type of family)
'extremely dreary and unpleasant' is the wordplay.
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'and' means one lot of letters go next to another.
'unpleasant' becomes 'nasty' (nasty can mean unpleasant or horrible).
'dreary' with its middle taken out is 'dy'.
'dy'+'nasty'='DYNASTY'
(Other definitions for dynasty that I've seen before include "Sequence of hereditary rulers" , "House" , "Song perhaps" , "Empire" , "Succession of relatives" .)