Gideon said his clan was the weakest in which tribe?

Answer: Manasseh

Gideon objected, "My clan is the weakest in Manasseh, and I am the youngest in my father's house" (KJV: "my family is poor in Manasseh").

““Please, my Lord,” Gideon replied, “how can I save Israel? Indeed, my clan is the weakest in Manasseh, and I am the youngest in my father’s house.””— Judges 6:15 (BSB)