Mythical man-bull (8)
I believe the answer is:
minotaur
'mythical man-bull' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for minotaur that I've seen before include "Bull-headed type" , "Labyrinth monster killed by Theseus" , "awful beast" , "Mythological man-bull" , "Mythical creature" .)