Knowing how to get off the ground (3)
I believe the answer is:
fly
'knowing' is the definition.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for fly that I've seen before include "needs to get away" , "Dipterous insect" , "Aviate" , "An insect; run away" , "SECOND PART OF 14" .)