killzone is turning into a pretty solid multiplayer game, right now they got a few classes such as medic, engineer, sniper, most of the basic stuff, the best part though is that once you achive a certain rank you get to mix classes.
As for clan support the game will have in game clan ladders, and ingame currency, for example to buy better guns or upgrades you have to perform well on the battlefield, being in a clan lets the entire clan share this currency, buy special clan upgrades. GAME IS GOING TO BE AWESOME.