you mean every1 using some sorta "sub class" system
Take it you havn't played Crusade Smavid?
Clan is seperate to guild. With clan you get your key boost (Sub-Class basically). But, it has been developed more so that you have clan wars, and the last man standing wins a clan ring i believe.
So no, it is not the same as a guild.
usually fps / rts = clan mmo/rpg/rp ect = guild