Cleo,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
.xitem {
width: 250px;
}
.value {
max-height: 3em;
overflow: hidden;
transition: max-height 1s;
}
.xitem.active .value {
max-height: var(--h);
}
</style>
</head>
<body>
<div class="xitem">
<div class="main">
<div class="tag">test</div>
<div class="value">Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen
book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged.
</div>
</div>
</div>
<div class="xitem">
<div class="main">
<div class="tag">test</div>
<div class="value">Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen
book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged.
</div>
</div>
</div>
<div class="xitem">
<div class="main">
<div class="tag">test</div>
<div class="value">Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen
book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged.
</div>
</div>
</div>
<script>
const items = document.querySelectorAll('.xitem');
items.forEach(item => {
item.addEventListener('click', (event) => {
if (event.target.closest('.tag'))
items.forEach(el => el == item ? el.classList.toggle('active') : el.classList.remove('active'))
})
let h = item.querySelector('.value').scrollHeight;
item.style.setProperty('--h', `${h}px`)
})
</script>
</body>
</html>