JSFiddle - React, Tailwind, and code Playground

HTML

<div class="dropdown">
	<a class="" href="#">Наведи на меня</a>
	<div class="dropdown-menu">
		<a class="dropdown-item" href="#">ССЫЛКА</a>
	</div>
</div>

CSS

.dropdown 
{
	display: inline-block;
}

.dropdown-menu 
{
	position:absolute;
	margin-top: 50px;
	opacity: 0;
	transition: margin-top 1s, opacity 1s;
}

.dropdown:hover .dropdown-menu 
{
	margin-top: 0;
	opacity: 1;
}

.dropdown-item 
{
	display:block;
	border-right: 5px solid #81d742;
	text-decoration:none;
}

.dropdown-item::before 
{
    content: '';
    z-index: -1;
    position:absolute;
    height: 100%;
	right: 0;
    background: #81d742;
	transition: 1s;
}

.dropdown-item:hover::before 
{
	left:0;
}