Problem overwriting parent css with child theme

I am trying to overwrite a theme using a child theme

Most of it is working fine but I have an issues with some css elements

I really want to clear a class and start again but can’t see how to do it

for example in my parent I have

.menu {
	background-color:#585858;
	background-image:-webkit-gradient(linear, left top, left bottom, from(#585858), to(#3d3d3d));
	background-image:-webkit-linear-gradient(top, #585858, #3d3d3d);
	background-image:-moz-linear-gradient(top, #585858, #3d3d3d);
	background-image:-ms-linear-gradient(top, #585858, #3d3d3d);
	background-image:-o-linear-gradient(top, #585858, #3d3d3d);
	background-image:linear-gradient(top, #585858, #3d3d3d);
	clear:both;
    filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#585858, endColorstr=#3d3d3d);
	margin:0 auto;
}

and in my child

.menu {
/*	background-color:#585858;
	background-image:-webkit-gradient(linear, left top, left bottom, from(#585858), to(#3d3d3d));
	background-image:-webkit-linear-gradient(top, #585858, #3d3d3d);
	background-image:-moz-linear-gradient(top, #585858, #3d3d3d);
	background-image:-ms-linear-gradient(top, #585858, #3d3d3d);
	background-image:-o-linear-gradient(top, #585858, #3d3d3d);
	background-image:linear-gradient(top, #585858, #3d3d3d);*/
	/*clear:both;*/
    /*filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#585858, endColorstr=#3d3d3d);*/
	margin:0 auto;
	float: right;
}

this doesn’t work as it doesn’t clear the commented out elements

What’s the best way todo this

Any help would be much appreciated