I believe what you want is to select the transaction(s) from sold and click
Other Action > Archive
alternatively for individual transactions you can click the dropdown arrow in the "Actions" column and select archive
This will remove them from the Sold category and store them in the Archive. You can't actually -delete- the transaction as it may be needed for referencing in the event of a complaint or refund. Over time ebay will sweep out the old stuff.
Not entirely sure why you'd want to do this, as most people need and want to keep transaction logs for business records...
Unless ofc you're scamming someone and think deleting it from your records will somehow cover your tracks, if that's the case you should know that isn't going to do anything at all for you.