You need a replacement cartridge. If not able to remove, take a photo of what sticks up with the handle removed and send it to us. If the cartridge is removed, take a photo as seen below and send to email@example.com
There are a few different scenarios that require different solutions. Take a photo underneath and indicate where the water is leaking, the hose, where the connect, or down the center where the pop up rod is. Email your photo and brief description to firstname.lastname@example.org
Once the color is tarnished from cleaner, hard water, etc the best option id refinish. We have an Original Equipment Manufacturer quality refinishing department for solid brass fixtures. Just email us your photos and color request for more information.
The cartridge is the replaceable part that controls the water on and off function. The valve body is what it screws in to, and usually doesn't need to be replaced.