You are probably referring to two different clipboards.
The Windows clipboard and the Office clipboard
Clear items from the Office Clipboard
[[If the Microsoft Office Clipboard is not displayed in the task pane, click
Office Clipboard on the Edit menu.
On the Office Clipboard task pane, do one of the following:
To clear one item, click the arrow next to the item you want to delete, and
then click Delete .
To clear all items, click Clear All]]
============
ClipBook Viewer overview
[[When you cut or copy information from a program, it is moved to the
Clipboard and remains there until you clear the Clipboard or until you cut
or copy another piece of information. The Clipboard window in ClipBook
Viewer shows the contents of the Clipboard. You can paste the information
from the Clipboard into any file as often as you like. However, the
information is only stored on the Clipboard temporarily.
You can also save the contents of the Clipboard to an individual Clipboard
file instead of a ClipBook page. These files generally have the extension
..clp and cannot be shared with others.]]