Clapping with one hand certainly requires practice, but can be very "handy" if you are holding items, have a wrist or hand injury, or find that your hands are otherwise occupied. There are several different ways to make your hands clap and a variety of sounds they can produce, from soft and dry finger snaps to powerful club bangers.
A great way to practise clapping with only one hand is to clap in place by placing your palm on the ground or other surface, and then making a fist that gently wraps your thumb around each of your fingers. You can then tap these fingers on your palm and listen to the sounds they make as they hit against the surface.
The sound pressure produced by different hand configurations can vary significantly, as shown in this chart from an acoustics research paper (click to download PDF). The loudest configuration - with the hands held at 45 degrees to each other and partially overlapping, with the thumbs slightly domed to enclose a pocket of air - generates a very brief pulse of low frequencies at the resonance points.
Be careful not to clap at inappropriate times, such as during a song or performance, or in a situation where it is not appropriate to do so. For example, it is considered rude to clap after music at some churches where choral performances are intended to be appreciated in a meditative and contemplative silence.