Some paper, off-white, with no heading (4)
I believe the answer is:
ream
'some paper' is the definition.
(a ream is an amount of paper)
'off-white with no heading' is the wordplay.
'off-white' becomes 'cream' (similar colours).
'with no heading' means to remove the first letter.
'cream' with its first letter taken off is 'REAM'.
(Other definitions for ream that I've seen before include "Quantity of paper, about 500 sheets" , "papers" , "Twenty quires of paper" , "500 sheets, perhaps" , "480 sheets of paper" .)