I thought it was a bit arcane, but not unprecedented, as I've previously seen it in cryptics. An Indy puzzle just last year and an Azed came up quickly.
For instance
https://www.google.com/search?q=%22Arpad+Elo%22+site%3A+fifteensquared.net
Given the brevity of the clue, the only well-known candidate was the reliable TAL, which had no chance of fitting. The only possible "prominent" player who came to mind was Iivo NEI, which I considered too specialised and didn't fit either.
So the solution arrived by process of elimination.