What would happen if a new predator was introduced to the food web that eats frogs

It depends on the population growth of such a predator, as well as if there are any natural predators in the food web, or if they are an ap-ex. If there is no direct predator for the "new predator", then it may lead to a reduction of primary consumers, which may affect not only the long-term population growth of the new predator, but also any other predators in the food webs. It will lead to a reduction of every population, and maybe even the collapse of the food web.