Reason to stop flying (6)
I believe the answer is:
ground
'reason' is the definition.
(I know that reason can be written as ground)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ground that I've seen before include "Powdered; land" , "what coffee might be" , "Terrain" , "Arena" , "crumbled" .)