Providing input to clipper circuits
The job of an ideal clipper is exactly that: clip. Any voltage exceeding a certain range is "cut back" to that range.

Thus, it doesn't really matter what kind of signal you feed in.

Note that just as any real-world signal, a real-world clipper has imperfections:

Bandwidth: If you design a clipping circuit that works well for signals from DC to say 20 kHz, and you feed in 200 MHz, then it's pretty much undefined what will happen. In reality, most systems are low pass filters to a certain degree, but it might very well be that 200 MHz just sees as diode in non-conductive mode as capacitor, and that's not much of a hindrance for high-frequency AC signals, for example!

Maximum voltage ranges: If you design a circuit say, based on diodes and low-voltage opamps, and you attach grid voltage, you're going to have a Bad TimeTM.

Especially the bandwidth restriction is an interesting one; the analog bandwidth of a square wave signal is theoretically infinite. In practice, it's not, because that square wave was produced by something that doesn't have infinite bandwidth. The clipper now having its own frequency-dependent behaviour will attenuate different parts of the signal differently, leading to a shape that isn't quite rectangular anymore. In reality, that's no problem: the math works out that typically, for not incredibly high frequencies, clipping a square wave just actually yields a square wave with lower amplitude, unless your clipping circuit was designed inappropriately.