There are several reasons why your SmartCite bibliography would need to be updated, such as changing your citation style or adding or removing citations from your paper. 

Note that SmartCite does offer automatic bibliography updates, which you can turn on within the Options of the SmartCite Add On:

But if you prefer manual updates, you can update your bibliography at any time by clicking the "update bibliography" button at the bottom of the bibliography pane:

To fully delete your bibliography from your document, hover your cursor over any area of your bibliography, and you'll see a grey box appear around it. Click to get a "Smartcite Bibilography" button on the upper left-hand side of your bibliography:

Once you've clicked on the "SmartCite Bibliography" button which will select your entire bibliography, simply hit "delete" on your keyboard.

You can add your bibliography back in at any time by selecting "update bibliography" at the bottom of the SmartCite bibliography pane: