Could you explain me the right form of the idiom "to come clean" and its connection with subject? I have found the expression "to come clean ABOUT" in both of my printed dictionaries. The same form states the web Merriam-Webster. But the Financial Times article headline looks like this: "Clinton needs to come clean OVER email fiasco". Is this any new version of preposition here? Thank you.
"come clean" is the idiom - it could be followed by "about", "over", "regarding", and various other words which are all synonyms in this context. They're not part of the idiom.