How to fix a leak in pipe valve?
If the leak is from under the nut at the handle, remove the nut and the handle. Under the handle may be a nut. If so this is a packing nut. Tighten the nut clockwise just a bit at a time until the drip quits. If there is no packing nut then replace the handle and tighten the nut for the handle: this nut could be doing double duty as a packing nut and to hold the handle on. If neither attempt stops the drip you may have to replace the valve.