Many sheets of paper are rewritten, as well as manuscript (5)
I believe the answer is:
reams
'many sheets of paper' is the definition.
(a ream is a large amount of paper)
'are rewritten as well as manuscript' is the wordplay.
'rewritten' indicates anagramming the letters.
'as well as' is a charade indicator (letters next to each other).
'manuscript' becomes 'ms' (abbreviation for manuscript).
'are' anagrammed gives 'rea'.
'rea'+'ms'='REAMS'
(Other definitions for reams that I've seen before include "This much paperwork" , "a very large amount" , "Scrapes the barrel" , "Lots of paper" , "Large quantities (of paper?)" .)