It happened at the 7-11 on Federal street and Marlton Pike around 3-am.
Investigators say an unidentified man walked into the store with a baton and demanded money.
The clerk then pulled out a knife.
After a confrontation, police say the suspect was stabbed twice in the chest.
He was pronounced dead at a local hospital.
The clerk is now being questioned.
No word yet if the clerk will face any charges.