Greek character devoured by child monster (8)
I believe the answer is:
minotaur
'monster' is the definition.
(I know that Minotaur is a type of mythical creature)
'greek character devoured by child' is the wordplay.
'greek character' becomes 'tau' (letter from the Greek alphabet).
'devoured by' indicates putting letters inside.
'child' becomes 'minor' (synonyms).
'tau' put into 'minor' is 'MINOTAUR'.
(Other definitions for minotaur that I've seen before include "Mythological man-bull" , "Creature, half-man and half-bull, slain by Theseus in the Cretan maze" , "Mythical man-bull" , "50 per cent ruminant" , "Cretan labyrinth resident" .)