Hi,
It depends if you are referring to the Suppliers list, you can order this list clicking on the "Supplier" column heading. IF you are referring to the supplier drop down when creating a purchase order, unfortunately, this cannot be arrange, but you can enter the first letters on the case to find it...
In regards to "clear the database as it is consumed", right click the item and select to delete, or update the item inventory manually, it depends on what you wish to accomplish.
Regards,