Bundle of grain (5)
I believe the answer is:
sheaf
'bundle of grain' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sheaf that I've seen before include "Bundle of cereal plants" , "A bundle, of corn stalks or papers" , "Bundle as of arrows or corn stalks" , "Bundle, of grain stalks say" , "Reaper's bundle" .)