JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.4.2/chosen.jquery.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.4.2/chosen.min.css">
<div id="home">

<fieldset>
<legend>#1
</legend>
  <div class="fieldset-content">
    <div>
    <select data-placeholder="Choose something" class="classname" name="somthinghere[]">
      <option value="123">Somthing</option>
      <option value="124">Somthing again</option>
    </select>
    </div>
    
    <button class="add_field_button btn btn-warning" data-fields="0" name="add">Add more selectfields and use the choosen plugin</button>
  </div>
</fieldset>

</div>

JavaScript

var x = 1 ;
 
 $(document).ready(function() {
   
   jQuery('#home select').chosen() ;
   jQuery(document).on('click','.add_field_button',function(e) {
   makeChosen(false) ;
     x++ ;
     e.preventDefault();
     var add_button = $(this);
     var fieldset = add_button.closest('fieldset');
     var newFieldset = fieldset.clone(true,false).appendTo('#home') ;
     newFieldset.find('select').append('<option value="">Test '+x+'</option>') ;
    newFieldset.find('legend').html(x) ;
     makeChosen(true) ;
   });
 });
 
 function makeChosen(status)
 {
 	if ( status ) jQuery('#home select').chosen() ;
  else
  {
  jQuery('#home select').chosen('destroy') ;
  }
 }