Using "hunter" as your noun is what's going to cause the trouble, as placing a noun before hunter usually implies it is the object of the hunt (e.g. "crocodile hunter", "big game hunter", "bargain hunter"). This rule is only relaxed in cases where that meaning is obviously unlikely and the opposite interpretation is the one more likely to make sense (e.g. "female hunter", "American hunter"). You're not going to be able to coerce the meaning of "werewolf" into being a likely participant in a hunt, so you'll have to search for an entirely different formulation.
This problem always exists to some degree when using the noun form of a transitive verb in English with a potential actor as its preceding adjective; the degree to which it is misinterpreted is entirely due to its common uses and context. For example, "race car driver" is unlikely to be a race car who is a driver, while "cattle drivers" is a reference to men who drive cattle, but could be used in a fantasy novel for a group of drivers who were cattle. I don't know if there is a formal term for this type of construction.
This therefore leads to possible solutions for your problem: use a formulation that does not include the noun form of a transitive verb. Instead of "hunter", for example, you might use "detective" or "private eye", neither of which would cause confusion if preceded by "werewolf".