Former British royal house (7)
I believe the answer is:
hanover
'former british royal house' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for hanover that I've seen before include "Royal house of Britain 1714-1901" , "German 22 Across" , "old house" , "9 [HOUSE]" , "10 [HOUSE]" .)