Hi Andrea,
Thank you for that code:)
This code is exactly but i want the clear icon only when the text enters into the text box, i have tried the below code but when i placed in my tool the padding-bottom is different in chrome but is working fine in IE and Mozilla. Please find the below jquery code and css code. for that.
            $("#S1aa_7_other").addClass("clearable x");
			function tog(v){return v? 'addClass':'removeClass';} 
$(document).on('input', '.clearable', function(){
    $(this)[tog(this.value)]('x');
	}).on('mousemove', '.x', function( e ){
    $(this)[tog(this.offsetWidth-18 < e.clientX-this.getBoundingClientRect().left)]('onX');
}).on('touchstart click', '.onX', function( ev ){
    ev.preventDefault();
    $(this).removeClass('x onX').val('').change();
	$("#S1aa_7_graphical").attr('class','graphical_select checkbox');
		SSI_SetSelect("S1aa_7", false);
});
 
<style type="text/css">
.clearable{
  background: #fff url('[%GraphicsPath()%]cross.bmp') no-repeat right -10px center;
  border: 1px solid #999;
  width: 160px;
  padding: 5px 17px 5px 4px;
}
.clearable.x  { background-position: right 5px center; } /* (jQ) Show icon */
.clearable.onX{ cursor: pointer; }              /* (jQ) hover cursor style */
.clearable::-ms-clear {display: none; width:0; height:0;} /* Remove IE default X */
</style>