A moral system and harsh aesthetic abandoned by the East (5)
I believe the answer is:
ethic
'a moral system' is the definition.
(I've seen this before)
'harsh aesthetic abandoned by the east' is the wordplay.
'harsh' indicates anagramming the letters.
'abandoned by' suggests deleting specific letters.
'aesthetic' with 'east' removed is 'hetic'.
'hetic' with letters rearranged gives 'ETHIC'.
'and' acts as a link.
(Other definitions for ethic that I've seen before include "Moral rule" , "Moral code" , "Principles accepted by a social group" , "System of principles" , "Moral practice" .)