Agrarian epoch crops twice in rotation outside (4-3)
I believe the answer is:
open air
'outside' is the definition.
(open air is a kind of outside)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for open air that I've seen before include "not doing covers?" , "kind of concert" , "Outdoors - with no cover" , "like 12 [CONCERT] in Hyde Park" , "Unenclosed space outdoors" .)