Grim utterance about dog (4)
I believe the answer is:
mutt
'dog' is the definition.
(mutt is a kind of dog)
'grim utterance about' is the wordplay.
'about' says the answer is hidden in the clue.
'MUTT' is hidden in the letters of 'grim utterance'.
(Other definitions for mutt that I've seen before include "Thematic type [DOG]" , "Mongrel dog - foolish person" , "far from best in show?" , "Mongrel - fool" , "Dog of mixed breed" .)