Slaughter ogre messily (4)
I believe the answer is:
gore
'slaughter' is the definition.
(thesaurus)
'ogre messily' is the wordplay.
'messily' indicates an anagram.
'ogre' anagrammed gives 'GORE'.
(Other definitions for gore that I've seen before include "Pierce or wound with a horn or tusk" , "Impale" , "Clotted blood" , "piece of material" , "Make a hole in" .)