The Delete Clips button is available on the AceText Tower and in the Edit menu. It is also available on the Recycle Bin toolbar. Pressing the Delete key on the keyboard while the list or tree of clips has keyboard focus also invokes the Delete Clips command.
Deleting clips from the ClipHistory or a collection moves those clips into the recycle bin. Deleting clips from the recycle bin removes them permanently.
See the Recycle Bin topic to learn the difference between restoring clips from the recycle bin and via the Undo command.