Stop round breathing space during descent (9)
I believe the answer is:
forestall
'stop' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for forestall that I've seen before include "Avert" , "Arrive first" , "Anticipate" , "Hinder by anticipation" , "Obstruct by taking advance action" .)