JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/css/bootstrap-select.min.css">

<!-- Latest compiled and minified JavaScript -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/js/bootstrap-select.min.js"></script>
<div class="form-group col-md-4">
    <label for="cSecretaria">Secretaria pertencente</label>
    <select class="form-control selectpicker" data-live-search="true" title="--" name="tSecretaria" id="cSecretaria">
        <option value="sec1">Secretaria 1</option>
        <option value="sec2">Secretaria 2</option>
        <option value="sec3">Secretaria 3</option>
    </select>
</div>

<button class="btn btn-primary" onclick="reseta()">Resetar</button>

JavaScript

function reseta() {
    $('select').val('').trigger('change');
}