figurehead
A leader in name only who has little real power.
A figurehead is someone who holds an important-sounding title or position but has little real power or authority. The term originally comes from sailing ships, which often had carved wooden statues (called figureheads) mounted on their bows. These decorative figures looked impressive but obviously couldn't steer the ship or give orders to the crew.
In government or organizations, a figurehead might have a fancy office and attend ceremonies, but other people make the actual decisions. Some countries have kings or queens who serve as figureheads: they represent the nation at official events and appear on currency, but elected officials run the government. In a school club, if the president just poses for photos while the vice president does all the real work, that president is acting as a figurehead.
Being a figurehead isn't always negative. Sometimes organizations need someone respected or beloved to represent them publicly while experts handle the complex decisions behind the scenes. But if someone discovers they're just a figurehead when they thought they had real authority, they might feel frustrated or deceived.