When a stripper inserts her middle finger into her anus and then places it into a customers mouth, without them being aware of where the finger actually was. This act is typically only done when the customer has upset the girl in some way, and usually used during a private dance.
Larry: Wow, that guy was a real asshole!
Cindy: He was so rude! That's why he got the Shelby Clam-Digger!