Clip-on means something is made to hold on with a clip, not with a pin, glue, a screw, or a hole through the body. You squeeze or slide the clip, and the thing stays put. People say it most about small wearables and tools: clip-on earrings (no piercing), a clip-on tie (the knot is already made; the clip bites the shirt collar), clip-on sunglasses that sit on ordinary glasses, a clip-on microphone on a collar, a clip-on light on a book or a bike. As an adjective it sits in front of a noun: clip-on earrings. As a noun, a clip-on is that kind of thing, often an earring or a tie. It feels practical and everyday, not fancy. Though actually the point is not “cheap” — a clip-on can be well made — the point is how it attaches: you can put it on and take it off without making a hole or tying a knot. Related idea: if something clips onto a belt or a bag, shops still often label it clip-on.