Answer:

grr

Answer	Crossword Clue
GRR	Sound for Tony the Tiger
GRR	Watchdog's warning
GRR	Pound sound

GRR	"Harrumph..."
GRR	[Annoooyyying]
GRR	Boxer's warning
GRR	Weimaraner's warning
GRR	Warning from a Westie
GRR	Pit bull's warning
GRR	Mutt-ered warning?
GRR	Watchdog warning

GRR	Ticked-off utterance
GRR	"That is so infuriating!"
GRR	"That really bugs me!"
GRR	Guard dog's sound
GRR	[How exasperating!]
GRR	Lab warning?
GRR	Shepherd's warning
GRR	Audible warning

GRR	"Don't mess with me!"
GRR	Lab's warning
GRR	Weimaraner warning
GRR	"Don't come through that gate!"
GRR	Warning from a watchdog
GRR	"Better stay out of my yard!"
GRR	Lab alert?
GRR	"I'm mad!"

GRR	Rover's warning
GRR	Canine warning that the answers to starred clues have in common, initially
GRR	Lab warning
GRR	Spot warning
GRR	Bear's threat
GRR	"That makes me mad!"
GRR	"One move and I bite!"
GRR	Airedale's warning

GRR	Hound's warning
GRR	White Fang's warning
GRR	"Make my day, mailman!"
GRR	Fido's warning
GRR	"I could just scream!"