Does it enable one to breathe while flying? (7)
I believe the answer is:
airline
'flying?' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for airline that I've seen before include "Transport organisation" , "Aircraft operating company" , "Virgin, possibly" , "carrier" , "Company operating aeroplanes" .)