Turning up full of hubris in the beginning, refer to moral belief (5)
I believe the answer is:
ethic
'moral belief' is the definition.
'turning up full of hubris in the beginning refer to' is the wordplay.
'turning up' shows that the letters should be reversed in order.
'full of' indicates putting letters inside.
'hubris in the beginning' becomes 'h' (I can't justify this - if you can you should give a lot more credence to this answer).
'refer to' becomes 'cite' (synonyms).
'h' put inside 'cite' is 'cihte'.
'cihte' written backwards gives 'ETHIC'.
Can you help me to learn more?
(Other definitions for ethic that I've seen before include "System of principles" , "Code of principles" , "Moral principle" , "Moral practice" , "Set of moral values" .)