Wallpaper purchase (4)
I believe the answer is:
roll
'wallpaper purchase' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for roll that I've seen before include "Move on wheels - individual portion of bread" , "Continuing success if one is on this" , "Go over and over" , "wind" , "Move like a ball" .)