Many papers covering large area of study (5)
I believe the answer is:
realm
'area of study' is the definition.
(I've seen this in another clue)
'many papers covering large' is the wordplay.
'many papers' becomes 'ream' (a ream is a large amount of paper).
'covering' means one lot of letters goes inside another.
'large' becomes 'L' (eg in clothes sizes).
'ream' placed around 'l' is 'REALM'.
(Other definitions for realm that I've seen before include "A Nation" , "Peers are possessed by this" , "Province" , "the UK, perhaps" , "region" .)