I would move the template outside of ul list. That way you can simply empty the list if you want to reset it.
HTML:
<script id="questionsTemplate" type="text/x-jquery-tmpl">
<span class="from">${source} </span>
</script>
<ul class="messagesList ifClicked">
</ul>
JS:
$(document).ready(function(){
var list = [ 'Routers', 'CNN', 'CNN' ];
var tmpl = '';
$.each(list, function(num, el) {
tmpl = $('<li>').html($('#questionsTemplate').html());
tmpl.find('.from').html(el);
$('.messagesList').append(tmpl);
});
});