Slowly diminish

ERODE

Think of how water or wind gradually wears away at rocks or land over long periods of time. The process often leaves behind smooth or altered surfaces.

Slowly diminish" hints at a gradual wearing away, which is exactly what "erode" means. The word often describes how water or wind breaks down rocks or land over time, fitting the idea of something fading little by little. There’s no hidden wordplay here—it’s a straightforward definition clue where the answer matches the meaning directly.