First create a new layer below the layer which you need to view restrictively. After creating the layer turn off the layer which you need to restrict the view.
Then you can view the newly created below layer intact. Then draw the mask in this new layer. To create this mask you can use any of marquee tool or draw object tools. But remember to fill the mask.
Then turn on the previously off layer. Follow the menu Layer > Create Clipping Mask. (Shortcut key is Alt+Ctrl+G)
If you need to release the clipping mask then select the masked layer and follow Layer > Release Clipping Mask menu.