If you have selected to add either the Analogue or Flip Clock widgets to your design, then these will act as ways of showing the current time within your content. By adding the widgets your screen will look as follows:
When you have added the widgets, when they are selected you will be presented with two additional tabs, these are Layer Basics and Analogue or Flip Clock Design. You can use the Layer Basics tab, as with any other zone, to set your widget positioning and set the arrangement of how the widget will appear.
By using either the Analogue Clock or Flip Clock Design tabs, you can specify the background colour of your choice, however, the option of transparency is not available in this instance.