Leaders of ancient unnamed region organised rituals around dawn (6)
I believe the answer is:
aurora
'dawn' is the definition.
('aurora' can be a synonym of 'dawn')
'leaders of ancient unnamed region organised rituals around' is the wordplay.
'leaders of' suggests taking the first letters.
The first letters of 'ancient unnamed region organised rituals around' is 'AURORA'.
(Other definitions for aurora that I've seen before include "Polar display" , "Dawn (literary)" , "Display of lights in the night sky" , "'... borealis, the northern lights (6)'" , "7 ... borealis, ... lights" .)