Large amount put on paper in set period (4,4)
I believe the answer is:
time slot
'set period' is the definition.
(a pre-arranged time for something)
'large amount put on paper' is the wordplay.
'large amount' becomes 'lot' (a lot of something).
'put on' is a charade indicator (letters next to each other).
'paper' becomes 'times' (The Times newspaper).
'lot' put after 'times' is 'TIME SLOT'.
'in' acts as a link.
(Other definitions for time slot that I've seen before include "Schedule period allocated to programme" , "Specified interval" , "It can be scheduled" , "limited period" .)