Dynasty that ruled empire in the past (7)
I believe the answer is:
hanover
'dynasty' is the definition.
(I've seen this before)
'ruled empire in the past' is the wordplay.
'ruled empire' becomes 'han' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in the past' becomes 'over' (both can mean finished or completed).
'han'+'over'='HANOVER'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for hanover that I've seen before include "9 [HOUSE]" , "German town, and royal house" , "British dynasty" , "Royal house from George I to Victoria" , "Victoria's House" .)