500 sheets of paper (4)
I believe the answer is:
ream
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">500 sheets of paper</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ream that I've seen before include "20 quires of paper" , "516 sheets of paper" , "Many bits of paper" , "Widen (hole) with borer; twenty quires" , "Widen (hole); quantity of paper" .)