Legendary source of magic flier (6)
I believe the answer is:
merlin
'flier' is the definition.
(merlin is a kind of birdanimal)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for merlin that I've seen before include "Legendary magician" , "Magician of the Round Table" , "BBC series" , "Hawk-like magician of Camelot" , "Bird of prey - magician" .)