"I'm buying this round"

ONME

["Think about the literal meaning of \"round\" as a shape, and where it might be positioned if it's \"on\" the speaker."]

The clue "I'm buying this round" leads to the answer "ONME" through a clever piece of wordplay. The phrase "this round" typically refers to a set of drinks in a social setting. However, in the context of the clue, "round" can also be interpreted as a shape, specifically a circle. When something is "on me," it means it is my responsibility or, in this case, resting on me. Therefore, if "this round" (a circular shape) is "on me," it literally means a circle is on me. The answer "ONME" reflects this literal interpretation, with "O" (a circular letter) being on "ME," thus forming "ONME."