Unique ruling as ordered (8)
I believe the answer is:
singular
'unique' is the definition.
(I know that unique can be written as singular)
'ruling as ordered' is the wordplay.
'ordered' indicates an anagram.
'ruling'+'as'='rulingas'
'rulingas' with letters rearranged gives 'SINGULAR'.
(Other definitions for singular that I've seen before include "Remarkable - unique" , "Unusual - not plural" , "Individual; extraordinary" , "One of a kind" , "distinctive" .)