Oregon-to-Idaho direction (4)
I believe the answer is:
east
'oregon-to-idaho direction' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for east that I've seen before include "Bidder after North (bridge)" , "Tom's friend" , "Where the sun rises" , "Bearing of ninety degrees" , "major point" .)