Rushing wind postponed start of mission (5-3)
I believe the answer is:
blast-off
'start of mission' is the definition.
(start of a space mission)
'rushing wind postponed' is the wordplay.
'rushing wind' becomes 'blast' (a blast of wind).
'postponed' becomes 'off' (off can mean cancelled).
'blast'+'off'='BLAST-OFF'
(Other definitions for blast-off that I've seen before include "Countdown finale" , "Rocket launch" , "Launch with great force, a spaceship perhaps" , "Conclusion of countdown?" , "The launching of a spacecraft - sounds explosive" .)