Mythical tale with sad ending (6)
I believe the answer is:
fabled
'mythical' is the definition.
(I've seen this in another clue)
'tale with sad ending' is the wordplay.
'tale' becomes 'fable' (I have seen 'Moral tale' mean 'fable' so perhaps 'tale' could also mean 'fable').
'with sad ending' becomes 'd' (I can't explain this - if you can you should give a lot more credence to this answer).
'fable'+'d'='FABLED'
Can you help me to learn more?
(Other definitions for fabled that I've seen before include "Enshrined in ancient stories or legends" , "Well-known" , "Mythical; imaginary" , "Legendary, mythical" , "Told of in legends or myths" .)