Function to change a plugin icon

functions.php

//Modify Timeline CPT
function wpse_65075_modify_timeline_menu_icon( $post_type, $args ) {
    // Make sure we're only editing the post type we want
    if ( 'te_announcements' != $post_type )
        return;
    
//     //Get labels and update them 
//     $labels = get_post_type_labels( get_post_type_object( $post_type ) );
//     $labels->name = 'Some things';
//     $labels->singular_name= 'Some thing';
//
//     //update args
//     $args->labels = $labels;
//     $args->label = $labels->name;

    // Set menu icon
    $args->menu_icon = 'dashicons-clock';

    // Modify post type object
    $wp_post_types[$post_type] = $args;
}
add_action( 'registered_post_type', 'wpse_65075_modify_timeline_menu_icon', 10, 2 );