When looking to expand on a topic or idea, there are numerous synonyms for the phrase "enlarge upon." Some of these synonyms include "elaborate," "develop," "extend," "amplify," "expound," "clarify," "illustrate," "exemplify," "flesh out," "digress," "prolong," "enrich," "embellish," "deepen," "enunciate," "delineate," "explicate," "unfold," and "enhance." All of these words indicate a desire to expand upon and provide more detail on a specific idea or topic. By using synonyms in your writing and speaking, you can create a more dynamic and engaging conversation or piece of content.