JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li><a href="#">Link 1</a></li>
    <li>
        <a href="#">Link with submenu</a>
        <ul>
            <li><a href="#">Sublink 1</a></li>
        </ul>
    </li>
</ul>

CSS

a:only-child { border: 3px solid red; border-radius: 10px; }