NOT A TEACHER
1. The online Merriam-Webster Learner's Dictionary reminds us that "scare away" is a phrasal verb." (In other words, it's a two-word verb. There are also some three-word phrasal verbs such as "I am trying to cut down on my calories.")
a. "scare" is the verb, and "away" is an adverb. (My note: Some books prefer to call it a "particle" when it is part of a phrasal verb.)
b. Some phrasal verbs (not all) can be separated. So you could say "The hunters scared the wild beasts away" or "The hunters scared away the wild beasts."
2. If you were diagramming that sentence using the Reed-Kellogg system, I think that you would use the second sentence to diagram, even though you might write/say the first sentence.
a. The "skeleton" of a diagram would be: "hunters scared away beasts." Then you would add the other words in order to come up with an acceptable English sentence.