In here, a modest quantity of paper (4)
I believe the answer is:
ream
'quantity of paper' is the definition.
(I've seen this before)
'in here a modest' is the wordplay.
'in' indicates a hidden word.
'REAM' is hidden within 'here a modest'.
(Other definitions for ream that I've seen before include "516 sheets of paper" , "Lots of paper" , "20 quires of paper" , "Widen out (bore)" , "Twenty quires of paper" .)