query by custom field from wp user frontend

Hi
How to query by custom field

<?php
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$ar = get_post_meta( $post->ID, 'oboz', true );
$args = array(
'order' => 'ASC',
'key'     => $ar,
'value'   => 'Letnie',
'compare' => '=',
'paged'=>$paged,
'posts_per_page' => 1,
);
$temp = $wp_query;
$wp_query = null;
$wp_query = new WP_Query( $args );
if ( $wp_query->have_posts() ) : ?>

Field named “oboz” is radio meta field with 2 values “Letnie” and “Zimowe”. I want to query “Letnie” so i compare this value to key “oboz” but it doesnt work… Of course query works without args – key, value, compare.

https://www.ads-software.com/plugins/wp-user-frontend/