If a selection has no history of a choice being made, you can remove it by clicking the “Delete item” link in the upper right corner of the selection item. There you will see the option to move any files, photos or comments that are part of the selection item, before it is deleted.
For everyone's protection, and to preserve the paper trail, you cannot delete a selection that has a history of a choice being made.
Instead, you can update the selection to include the "Option to Decline" and then choose the “I don’t want this selection” choice.