"Clued in" is an informal phrase that means someone is aware of what is going on or has been informed about something. The word "knowledgeable" is the most straightforward synonym as it pertains to having knowledge about a particular subject. "Informed," "aware," and "conscious" also express similar meanings. Other possible synonyms are "up-to-date" and "well-informed," which describe someone who has current information or has done their research. "Savvy" is another word that describes someone who is experienced or knowledgeable in a particular area. Overall, there are several synonyms for "clued in" that convey similar meanings in different contexts.