Your code has bracket misplaced and halt used unnecessarily. This is the edit:

on *:TEXT:!chatclear:#:{   
  if ($nick isop #) {
    tokenize 44 /clear, $+ $nick has cleared the chatroom!
    msg # $*
  }
  else { 
    .notice $nick you  not authorized to use this command 
  } 
}

You can tokenize it so you only need one msg command.