Barn's upper space (4)
I believe the answer is:
loft
'barn's upper space' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for loft that I've seen before include "Raised shelter for pigeons" , "Storage space under a roof" , "Elevation" , "Space under barn roof for storing hay" , "Shelter for racing pigeons" .)