Both. You almost always need both.

Clipping deals with geometry that is partially inside the camera. Culling (either for backfaces or entire instances) is a preliminary performance optimization that can be performed in a variety of ways.

As an example, if you're writing a shooter then the floor might be a large square that will almost definitely be intersecting the near plane. You absolutely need clipping here.

This is precisely the first place I realized I needed proper clipping. Wasted many hours trying to hack my way out of doing it the right way.