You will need a file open, with at least one layer with content (a sketch, an ink drawing, a photo, and so on) inside of it. You will also need an active selection, such as the one made by the Selection pen in the Using the Selection pen recipe.
How to do it…
Select the Marquee(M) tool from the toolbox. Then, select the Clear selection subtool.
Draw over the area to be deselected. The area will be highlighted in green, as shown here:
When the mouse button or stylus is released, the highlighted area will be subtracted from the currently active selection, as shown in the following screenshot: