I restate revised dissertation (8)
I believe the answer is:
treatise
'dissertation' is the definition.
(I've seen this before)
'i restate revised' is the wordplay.
'revised' is an anagram indicator.
'i'+'restate'='irestate'
'irestate' with letters rearranged gives 'TREATISE'.
(Other definitions for treatise that I've seen before include "formal document" , "Learned work on particular subject" , "Long, detailed essay" , "Disquisition" , "Written composition" .)