A new broom sweeps clean.

Someone newly appointed to a role often begins with energy, discipline, and a determination to remove problems that others have tolerated.

The saying can praise a fresh start, but it may also imply that early zeal is temporary; the surrounding tone determines whether it is approving or skeptical.

Used when a newcomer quickly imposes order or makes changes, especially after taking charge of a workplace, team, or household. Depending on tone, it can be approving or mildly skeptical about whether the improvement will last.