If you mean a Dardanus megistos or a related species hermit crab, then I wouldn't chance it. They have been know to eat fish, and wartskin anglers aren't exactly the most capable of escaping from danger. In fact, as I understand it, if you're going to keep tankmates with an angler, you want them to be both inedible and peaceful - I've heard of tankmates essentially stressing anglers to death by picking at them, so they really need to be peaceful and nonaggressive. Giant hermit crabs are inedible for the angler, but not super peaceful. The reverse is likely also true for the angler, edible for the crab, but super peaceful.