Why is my "clip adjustment layer to layer below" button greyed out?

Question

I'm trying to set an adjustment layer to clip to an entire group of layers, but the button is greyed out.

How can I do this? Why is the option greyed out?

(Photoshop CS5)

Answer 1

I do not have your version but...Try this:

Hold the Alt key and click between the Layers: Adjustment and Group 1.

This will create a clip.