Trio of myth (5)
I believe the answer is:
fates
'trio of myth' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for fates that I've seen before include "Mythological goddesses controlling destinies" , "Three Greek goddesses who presided over life and death" , "Classical goddess trio" , "classical goddesses" , "Goddesses governing human lives" .)