Hold down Option, position the pointer
over the line dividing two layers in the Layers palette (the pointer
changes to two overlapping circles
), and
then click.
In the Layers palette, select the top layer of a pair of layers you want to group, and choose Layer > Group With Previous.
The layers in the clipping group have the opacity and mode attributes of the bottommost base layer in the group.
If you need to change the stacking order of the
clipping group relative to other layers in the image, select all
layers in the group, then drag the group’s base layer up or down
in the Layers palette. (Dragging a layer without selecting all the
layers in the group will remove that layer from the group.)