Get the Toolkit Access group assigned to a post within a loop and verify if currently logged-in user has permissions to access the list.

toolkit-access-check-user-access.php

<?php
// -----------------------------------------------------------------------------
// Usage: place the function in functions.php
// Then call it from within the loop in the theme index.php, single.php etc.
// while ( have_posts() ) : the_post(); if (iseek_user_access() ):
//  ... secret content goes here
// endif;
// -----------------------------------------------------------------------------


// Check if current user has permissions set in Toolkit Access plugin
// Warning: only one group is allowed per post. It will not work for multiple groups.
function iseek_user_access() {
	global $current_user;
	wp_get_current_user();

	// Get current user ID
	$userId = get_current_user_id();

	// Get the group assigned to the current post
	$post_meta = get_post_meta( get_the_ID() );
	$access_group = $post_meta['_wpcf_access_group'][0];

	if($access_group){
		// check if user belongs to the group
		$access_option = get_option("wpcf-access-types");

		// get the array of users who belong to $access_group
		$permitted_group_users = $access_option[ $access_group ]['permissions']['read']['users'];

		// Check if the currently logged-in user is on the accepted users list
		return in_array( $userId, $permitted_group_users ) ? true : false;
	} else {
		return false;
	}
}