So, i use Permissionns 3.x but my players (they add three node (anyone,leader and the last one exept mod)) but they can't do /clan, 'You don't have permissions to do that'. But i'm not op and i still can use /clan so i don't know where the probleme is... (i use the last version of simpleclan)

Read here, and use the appropriate node groups for your permissions system:

http://dev.bukkit.org/server-mods/simpleclans/pages/permissions/