Flesh-eating monster revealed in Progress (4)
I believe the answer is:
ogre
'flesh-eating monster' is the definition.
'revealed in progress' is the wordplay.
'revealed in' says the answer is hidden in the clue.
'OGRE' is hidden in the letters of 'progress'.
(Other definitions for ogre that I've seen before include "Cruel, fearsome person" , "Grim(m) beast?" , "Ergo (anag.)" , "Fairy tale giant" , "bad-tempered person" .)