Pilot with long limbs, good at higher altitude (7)
I believe the answer is:
biggles
'pilot' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for biggles that I've seen before include "Fictional Royal Flying Corps hero" , "Pilot" , "W. E. Johns's flying ace" , "Hero of books by WE Johns" .)