It's a beast, boys! (6)
I believe the answer is:
jackal
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for jackal that I've seen before include "Wild canine of Africa and southern Asia" , "Slender wild dog" , "Canine animal" , "Nocturnal dog-like predator" , "Dog-like African and Asian predator" .)