We have ignition, as conversely happens with meltdown (3,7,2)
I believe the answer is:
all systems go
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for all systems go that I've seen before include "Everything functioning correctly" , "Fully prepared to start" , "Ready for lift-off!" , "Everything is working" , "Everything's ready" .)