I, a setter, revised work (8)
I believe the answer is:
'work' is the definition.
(I have seen 'formal work' mean 'treatise' so perhaps 'work' could also mean 'treatise')
'i a setter revised' is the wordplay.
'revised' is an anagram indicator.
'iasetter' is an anagram of 'TREATISE'.
(Other definitions for treatise that I've seen before include "theory" , "Learned work formally dealing with a subject" , "Written study" , "Tract, monograph" , "A written work about treaties" .)