Use delete_post_meta to delete a value.
Example:
delete_post_meta($post->ID, 'brk_news_update');
If you want to update it, then use update_post_meta
update_post_meta($post->ID, 'brk_news_update','value');
Use delete_post_meta to delete a value.
Example:
delete_post_meta($post->ID, 'brk_news_update');
If you want to update it, then use update_post_meta
update_post_meta($post->ID, 'brk_news_update','value');