Outdoor spigot replacement - help

Please bear with my lack of knowledge in Plumbing... I have a thin copper pipe coming out of my home, with an attachement at the end connected to the handle to increase or decrease water pressure. When I put the water on, the water is coming out of this "attachment" . I think there is a crack in it. I tried to take this off since it is a hexagon shape, I put a wrench around this and another wrench on the thin pipe behind it. The problem is I cant get it off, and Im afraid of damaging the pipe behind it. Does anyone know if this attachment with the valve is supposed to screw off , or do I cut it with a hacksaw, right behind it and put a new one(with valve) on? Any assistance would greatly be appreciated. --Apologies for the vagueness.

Can you possibly post a photo of the "attachment".

It may be a valve that is soldered to the pipe. Or......

Sure, I will try to take a picture tonight and post it tomorrow.
Thanks

This sounds like a frostproof faucet. If so, it is a one piece unit that is connected to the water supply line inside the house. These are usually about 12" to 14" long. To safely remove it, you must use two wrenches inside where the unit connects to the house supply line. One wrench to hold the supply line so that it won't twist when pressure is applied to the faucet with the second wrench. It's not a highly technical job, but getting access to the pipe can be challenging in some cases. I have a basement when my plumbing is, so it's much easier than if it were a crawlspace. Replace the faucet in reverse of removal.

valve

The vagueness could get you into a lot of trouble. We do not know what the valve is, how it is attached, how to remove it, or even what to remove, and if you cut it with a hacksaw you could create a major problem for the plumber you would have to call to repair it.