Clean Whistler 

When one drops a dookie and it scant leaves a trace.

Toilet paper is hardly necessary after passing a clean whistler.

Clean Whistler by Country Mitch November 5, 2021

Clean as a whistle 

When you wipe your butthole after taking a dump and the toilet paper comes away stain free.

Hey man, i just took a huge dump but i was too tired to wipe my ass, good thing i was clean as a whistle

Clean as a whistle by slippychunks September 29, 2010

Clear as a whistle 

Super clear. Like “clean as a whistle”, but with clear. Very, very clear. Obvious.

There was no question that the Atlanta Falcons were the best team in the NFL. It was clear as a whistle.

Clear as a whistle by Fbabie11 October 29, 2017