The phrase 'clean forgotten' refers to something that has been completely forgotten or is no longer remembered. There are many synonyms for this phrase, including 'completely forgotten,' 'lost in oblivion,' 'oblivious,' 'unnoticed,' 'ignored,' 'overlooked,' 'ignored,' 'faded from memory,' and 'vanished without a trace.' Each of these synonyms can be used to describe a situation where something has been forgotten or overlooked, and they can be used in a variety of contexts. Whether you are talking about a forgotten item or a forgotten memory, there are many different ways to describe it.