Barn's upper level (4)
I believe the answer is:
loft
'barn's upper level' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loft that I've seen before include "Uppermost room" , "Attic" , "Throw up; pigeon house" , "Raised shelter for pigeons" , "Shelter for racing pigeons" .)