Wings of vulture and of raven under those of weighty mythological flier (6)
I believe the answer is:
wyvern
'wings of vulture' is the definition.
The definition suggests a singular noun which matches the answer.
'of raven under those of weighty mythological flier' is the wordplay.
I cannot really see how this works, but
'flier' could be 'ern' (ern is a kind of birdanimal) and 'ern' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'and' is the link.
Can you help me to learn more?
(Other definitions for wyvern that I've seen before include "1950s Vauxhall model" , "Fabulous creature" , "Heraldic device" , "Fire-breathing dragon with a snake's tail" , "In heraldry, a dragon with wings, two legs and a barbed tail" .)