a leading light
A person who is well-respected and viewed as important to a group. As a leading light of the human rights organization, he helped improve working conditions for millions of people around the world.
a leading lightmainly BRITISH
COMMON If someone is a leading light of an organization or group, they are one of the most important, active, and successful people in it. He is a leading light in the campaign to rid football of racism. She had been a leading light in the amateur dramatic society in Kuala Lumpur. Note: A leading light was a light which was placed at the entrance to a harbour or shallow channel of water, as a guide for ships.