Shortage of wind -- oxygen needed for asthmatic initially (7)
I believe the answer is:
drought
'shortage' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for drought that I've seen before include "Period with little rain" , "Aridity" , "Lack of rain" , "Period of low rainfall" , "Lack of rainfall" .)