Olympian trio running faster mostly (5)
I believe the answer is:
fates
'olympian trio' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'running faster mostly' is the wordplay.
'running' is an anagram indicator (the letters run around to different places).
'mostly' means to remove the last letter (most but not all of the word).
'faster' with its final letter taken away is 'faste'.
'faste' anagrammed gives 'FATES'.
Can you help me to learn more?
(Other definitions for fates that I've seen before include "Goddesses governing human lives" , "Lots" , "Goddesses guiding human lives" , "Mythological goddesses controlling destinies" , "Three Greek goddesses who presided over life and death" .)