Restrict access to a section of the site implemented by a custom module
If you implement hook_permission in your custom module, you can control the access of your client administration section.


Set up roles. You've done this already with the client role.
Implement hook_permission():

function MODULE_permission()
{
    return array(
        'access client administration' =&gt; array(
            'title'       =&gt; t('Access Client Administration'),
            'description' =&gt; t('Allow users to access client administration'),
        ),
    );
}

When you define hook_menu(), make sure you set the permissions accordingly:

function MODULE_menu()
{
    $items['client_administration'] = array(
        'title' =&gt; 'Client Administration Page',
...
        'access arguments' =&gt; array('access client administration'),
    );

    return $items;
}

Go to admin/people/permissions and set the permissions for 'Access Client Administration' to your client role.