If statement to check for post_content

The following line is wrong

<?php echo get_post_meta($partner->ID, $a_description, true); ?>

If you look closely, you are actually passing

get_post_meta($partner->ID, "a_description")

to the $key parameter of get_post_meta as this is the value assigned to $a_description

You should most probably change $a_description to just a_description

EDIT

This line

<?php echo get_post_meta($partner->ID, $a_description, true); ?>

should most probably be

<?php echo get_post_meta($partner->ID, 'a_description', true); ?>