Single piece of paper (5)
I believe the answer is:
sheet
'single piece of paper' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sheet that I've seen before include "Sail-rope on the bed?" , "Piece of linen; ship's rope" , "Piece of linen, paper, etc" , "Piece of paper or bedlinen" , "Page of postage stamps" .)