Leaders of young aviators couldn't handle this craft (5)
I believe the answer is:
yacht
'craft' is the definition.
(yacht is a kind of craft)
'leaders of young aviators couldn't handle this' is the wordplay.
'leaders of' indicates taking the first letters.
The initial letters of 'young aviators couldnt handle this' is 'YACHT'.
(Other definitions for yacht that I've seen before include "Fast sailing vessel" , "Pleasure craft" , "Cathy (anag.)" , "Pleasure-boat" , "Light, fast sailing-vessel" .)