A ruling's remarkable outcome (8)
I believe the answer is:
singular
'outcome' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'a ruling's remarkable' is the wordplay.
'remarkable' indicates anagramming the letters.
'a'+'rulings'='arulings'
'arulings' with letters rearranged gives 'SINGULAR'.
Can you help me to learn more?
(Other definitions for singular that I've seen before include "Individual; extraordinary" , "Unusual, maybe unique" , "Extraordinary, with reference to one" , "Unique, peculiar" , "Remarkable; not plural" .)