Obviously, cutting out and replacing the leaking fitting is the proper repair. But, there is plastic epoxy available at places like the home depot that is made for plastic. It's even white in color. Mix two parts together and apply. It's in a thick liquid form and comes in a type of syringe that squeezes out the proper amount of each. Just make sure the plastic is clean and dry. It works great.
Slathering pvc glue outside the joint almost never works, and silicone is a little better but looks horrible and usually leaks over time. (Kinda like how bathtub caulk gets moldy)
Are you sure it's even glued? Maybe the plumber missed that joint? The first thing I'd probably do is try to pry it apart if there is room.