Rank group of houses (6)
I believe the answer is:
estate
This clue is a double definition.
'rank' is the first definition.
(thesaurus)
'group of houses' is the second definition.
(I've seen this before)
(Other definitions for estate that I've seen before include "All that one owns at death" , "Extensive landed property (6)" , "Condition" , "The whole of a deceased person's assets" , "All of one's assets after death" .)