Definition
To be important or influential within a small or limited sphere, but not in a larger context.
He was a big fish in a small pond in their town, but nobody knew him in the city.
She may be a big fish in a small pond as the head of the local club, but on a national level, she's just a regular member.
He used to be the boss of this small company, but after joining a large corporation, he found himself just one of many.