Folded sheet of paper (5)
I believe the answer is:
folio
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">folded sheet of paper</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for folio that I've seen before include "Folded sheet - or book made from such" , "Book size" , "Book made of folded sheets" , "Sheet of paper folded to make two book leaves" , "Manuscript sheet" .)