<div id="accordion">
<div class="card border-0 mb-4">
<div class="card-header p-0 border-0 bg-transparent">
<a class="card-link h4 text-dark font-secondary d-block tex-dark mb-0 py-10" data-toggle="collapse"
href="#collapseOne">
<i class="fa fa-minus text-primary mr-2"></i> Accordion
</a>
</div>
<div id="collapseOne" class="collapse"
data-parent="#accordion">
<div class="card-body text-color pl-4 pb-0">
Lorem ipsum dolor sit amet.
</div>
</div>
</div>
</div>
.card-header used for some extra styling.
Icon is styled on data-toggle="collapse" attribute. So you dont have to use another classes.