<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<input type="radio" name="block" id="one"/>
<div class="cont">Текст</div>
<script>
if (document.getElementById('one').checked == true) {
document.getElementByClassName('cont').style.display = 'none';
}
</script>