fess up vs make a clean breast of

fess up and make a clean breast of both are verbs.

Word	Noun	Adjective	Verb	Adverb
fess up	No	No	Yes	No
make a clean breast of	No	No	Yes	No

As verbs, fess up and make a clean breast of are synonyms defined as:

fess up and make a clean breast of: admit or acknowledge a wrongdoing or error

Other synonyms of fess up include own up.

fess up (verb)	make a clean breast of (verb)
admit or acknowledge a wrongdoing or error	admit or acknowledge a wrongdoing or error