This is called a manifold hose. There is a bolt which holds this hose to the A/C compressor. While it is possible that this bolt loosened up, there are "O" ring gaskets sealing the joint between the 2 parts. The better "O" rings are made of silicone. Some of the cheaper "O" rings are made of materials which can break down and deteriorate.

There is a process called "evacuation" which requires using an electric Vacuum pump after you open the system. You will probably be better off removing the original O rings and replacing them with high quality new parts. A failed attempt to tighten the current bolt may result in shearing the bolt off. And even if you can tweak the bolt, the old parts may still leak.

The most expensive part of this repair will be the Freon. I imagine the O rings will be a few dollars. You can borrow a Vacuum pump from some Auto parts stores under their loaner programs. I would not bother removing the compressor to flick the old parts out.

Freon is often cheaper at K-mart, or Big-lots. I hope this helps you.