Stationer Sid revised thesis (12)
I believe the answer is:
dissertation
'thesis' is the definition.
(I know that thesis can be written as dissertation)
'stationer sid revised' is the wordplay.
'revised' is an anagram indicator.
'stationer'+'sid'='stationersid'
'stationersid' anagrammed gives 'DISSERTATION'.
(Other definitions for dissertation that I've seen before include "writing" , "thesis" , "Essay for a degree or diploma" , "scholarly work?" .)