The Clone Brush is very important to learn for graphic work.  I know that many people are either afraid of it or don't quite understand how it is used.  What you are doing is picking up part of an image with the brush and putting it somewhere else.  This is very useful when a little part of an image is missing and you need to fill it in.  But before you click on the Clone Brush, make sure you have the Texture boxes set to Null or else.........well, look below.  With the Opacity set to 100%, you should be getting solid brown from right clicking on the brown of the clock.  Instead you have a faint brown with texture.  That's because the Clone will apply a texture with the section of solid brown you were trying to copy.

So let's say your clock is missing a piece.  You want it to be filled in solid, so set the Opacity high, 100% in this case.  Many people make the mistake of trying to Clone too big, so start small as you learn.  In this case, a 5 pixel brush will be just fine.  Right click right below the area that needs to be filled in.  Now move the brush up and into the blank area.  Left click.  It will drop the same shade of brown into that missing area.  You may have to repeat this twice to fill completely.  Each time you want to drop in a clone, first right click on the spot where you are picking up the clone.  So right click to pick up, left click to drop in.

You can achieve some interesting effects by playing with the Clone.  I upped the size of the brush to 50 so that it covered the clock face area.  Notice also the Hardness is set to 50.  I right click on the clock face, then left click above the clock.  That's a nice little effect!