Gold and rosy rays split the dawn (6)
I believe the answer is:
aurora
'the dawn' is the definition.
('aurora' can be a synonym of 'dawn')
'gold and rosy rays split' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'and' is a charade indicator (letters next to each other).
'rosy rays split' becomes 'rora' (I am not sure about this - if you are sure you should believe this answer much more).
'au'+'rora'='AURORA'
Can you help me to learn more?
(Other definitions for aurora that I've seen before include "Roman Godess of the Dawn" , "dawn arrives" , "Dawn (literary)" , "Ship that turned red" , "Atmospheric phenomenon consisting of bands of light" .)