This will trigger if someone types c in a chatroom that you aren't a mod in...
Try something like

ON @*:text:c:#: {
 if ($nick isop #) { 
 .timerclear 1 1 msg # .clear 
 .timerclear 1 5 msg # $nick has cleared the chat.
}
else { describe Permission denied }
}

This will make it so that. you have to be op'ed (modded). and rather then using multiple messages quickly in a row it waits a few seconds to say "$nick cleared the chat"

.clear in JTV is the same as doing a /clear in jtv.