Grim utterance about dog (4)
I believe the answer is:
mutt
'dog' is the definition.
(I know that mutt is a type of dog)
'grim utterance about' is the wordplay.
'about' indicates the answer is hidden within the clue (the clue goes around or about the answer).
'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" .)