Why would a car stall only when the clutch is pressed in?

A car may stall when the clutch is pressed in if the engine is not receiving enough fuel or air, leading to a drop in RPM. This can occur due to issues such as a faulty idle air control valve, a dirty throttle body, or problems with the fuel system. Additionally, if the clutch is worn or not disengaging properly, it may create excessive load on the engine. It's essential to diagnose the specific cause to prevent stalling.