JSFiddle - React, Tailwind, and code Playground

HTML

<div id="leftNav">
        <ul>
            <li><a href="#"><span>A </span><span class="subTitle">Subtitle</span></a></li>
           <li><a href="#"><span>B  </span><span class="subTitle">Subtitle</span></a></li>
           <li><a href="#"><span>C  </span><span class="subTitle">Subtitle</span></a></li>
           <li><a href="#"><span>D  </span><span class="subTitle">Subtitle</span></a></li>
           <li><a href="#"><span>E  </span><span class="subTitle">Subtitle</span></a></li>
        </ul>
</div>

CSS

#leftNav ul li a span.subTitle
{
   
   font-size:       12px;
    color: red;
    text-decoration: none;
}