They might have a better chance of being one, but I'd say that only the people who actually add something to the community (organise events, clots, streams or things like Muli's user script) might be called "leaders". Even then their behaviour is important.
Of course those are leaders too; they are not mutually exclusive. But a leading competitive clan will always be a leader in its community, and its players will always represent that entity -- for better or for worse. That's true of all clans, of course: your players will always be representing your group, because anything they do, will have your clan tag next to it. That is a responsibility both the player and the clan has to accept, and if a player badly represents a clan, repeatedly, then it must decide whether it can continue to support that player's behavior.
Anyway. I know my thoughts aren't perfect, but I hope they at least make sense.