Predator one across upset (4)
I believe the answer is:
wolf
'predator' is the definition.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for wolf that I've seen before include "Howling canine that hunts in packs" , "Carnivore -- breed of 13 down" , "Devour ravenously" , "Pack animal; composer" , "gorge" .)