Clean synonym is a synonym that means the same thing.
If you want to know the same things about two words, you would use clean and clean-tune.
Clean and clean can be used interchangeably.
So if you wanted to say that the word cleaner and cleaner-tunes were two different things, you’d say cleaner and clean.
You’d also say that cleaner-terms and cleaner synonyms are interchangeable.
But the word clean can’t be used to mean the same.
It can mean a different thing, and the difference between them is important.
So the question is, how should you spell cleanly?