"Hang on to" is a versatile phrase that can be replaced with several synonyms to convey the same meaning. One such synonym is "cling to", which implies a strong grip or attachment to something. Another alternative is "retain", suggesting the act of holding onto an object, idea, or belief. Additionally, "grasp" can be used to signify a firm hold or understanding of something. Alternatively, "preserve" can be employed to describe the act of maintaining or safeguarding a particular item or concept. Lastly, "keep" can be a suitable synonym, denoting the act of holding onto something with care and not letting go.