Classic high flier who came unstuck (6)
'classic high flier' is the definition.
'icarus' can be an answer for 'flier' (I have seen 'Foolhardy flier ' mean 'icarus' so perhaps 'flier' could also mean 'icarus'). I'm unsure of the 'classic high' bit.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for icarus that I've seen before include "He died flying", "High-flyer in Greek mythology", "Daedalus's son", "In Greek myth, he flew too close to the sun and died", "Ill-fated flyer of myth".)