Crossword Genius

Not rocket science when weapon's bound to fly off, airborne (2-7)

Ross

I believe the answer is:

no-brainer

I'm a little stuck... Click here to teach me more about this clue!

'not rocket science when weapon's bound to fly off' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'airborne' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'airborne' is 'obrainer' which is located in the answer.
A single letter 'n' remains which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for no-brainer that I've seen before include "An easy decision" , "Something requiring little or no mental effort" , "It's totally clear" , "Something involving little or no mental effort" , "Trivial problem" .)

I've seen this clue in the Sydney Morning Herald.
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