Wikipedia's URL ender

ORG

Think of the three-letter suffix for non-profit websites, often seen after the dot in addresses for educational or community-driven platforms.

The clue refers to the last part of Wikipedia's web address, which is ".org." Most people recognize Wikipedia's full URL as "wikipedia.org," where "org" is the top-level domain (like .com or .net) that identifies it as an organization. The answer is simply the three-letter abbreviation for that domain, making it a straightforward fill-in.