Iron brace fixed without carbon, like a hang-glider must be (8)
I believe the answer is:
airborne
'like a hang-glider must be' is the definition.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for airborne that I've seen before include "Off the ground" , "as birds often are" , "upwardly mobile" , "In flight after taking off" , "so, paras?" .)