They're light enough to fly! (6)
I believe the answer is:
sparks
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 sparks that I've seen before include "Glowing particles for a colloquial radio operator" , "Fiery particles emitted by fire" , "Momentary flashes of light" , "Flashes from electrical discharge" , "Radio officer" .)