<?php

function filter_tribe_events_widget( $args ) {
    $args = array(
        'eventDisplay' => 'upcoming',
        'posts_per_page' => $limit,
        'meta_key' => '_ecp_custom_1',
        'meta_value' => 'Featured',
    );

    return $args;
}

add_filter( 'tribe_events_list_widget_query_args', 'filter_tribe_events_widget' );