Some bed linen he's put outside (5)
I believe the answer is:
sheet
'some bed linen' is the definition.
(sheet is a kind of bed linen)
'he's put outside' is the wordplay.
'put' becomes 'set' (both can mean to place or position).
'outside' means one lot of letters goes inside another (some letters go outside others).
'he' placed inside 'set' is 'SHEET'.
(Other definitions for sheet that I've seen before include "Piece of paper; nautical rope" , "Sail-rope on the bed?" , "Single piece of paper" , "Piece of linen; ship's rope" , "Piece of paper, linen, or water" .)