profess vs fess up

profess and fess up both are verbs.

Word	Noun	Adjective	Verb	Adverb
profess	No	No	Yes	No
fess up	No	No	Yes	No

As verbs, fess up is a hyponym of profess; that is, fess up is a word with a more specific, narrower meaning than profess:

Other hyponyms of profess include make a clean breast of, own up.

profess (verb)	fess up (verb)
practice as a profession, teach, or claim to be knowledgeable about	admit or acknowledge a wrongdoing or error
take vows, as in religious order
admit (to a wrongdoing)
confess one's faith in, or allegiance to
state insincerely
receive into a religious order or congregation
state freely