The phrase "face up it" can be replaced with several synonyms, depending on the context. If the intention is to take responsibility for something, one could say "own up to it" or "admit it." Similarly, "fess up" is a more informal synonym for taking ownership of one's actions. If the phrase is being used to discuss confronting a problem or challenge, "tackle it" or "deal with it" are both suitable alternatives. In a more positive context, "face it head-on" or "meet the challenge" can imply a sense of determination and courage. Ultimately, the choice of synonym depends on the tone and context of the sentence.