How to hide option in drop down menu?

I’m trying to hide the "Select Value" option in the drop down menu of a plugin I have for my wordpress, I’ve tried the following code:

div.calc-drop-down-box.calc_dropDown_field_id_0 {
    
            visibility: hidden !important;

}

But this doesn’t work. What am I doing wrong?

>Solution :

Try this:

.calc-drop-down.ccb-appearance-field.ccb-field option:first-child {
  display: none;
}

It gets the first child of type ‘option’ and hides it from the dropdown
https://jsfiddle.net/shn5dcmu/1/