shorthand syntax for custom fields

You have a couple of flaws in your code

• get_post_meta( 'fap_referral_link' ) should be get_post_meta( $post->ID, 'fap_referral_link', true ). Please see get_post_meta()

• You should always first check if you actually have posts before you run your foreach loop

• Never ever use extract(). It uses eval() which stand for EVIL. This has been completely removed from WordPress core years ago due to a specific reason. It poses a big security thread. Please consult the Shortcode API for correct use. Here is an example straight from the codex on how to use a shortcode

  // [bartag foo="foo-value"]
  function bartag_func( $atts ) {
      $a = shortcode_atts( array(
          'foo' => 'something',
          'bar' => 'something else',
      ), $atts );
  
      return "foo = {$a['foo']}";
  }
  add_shortcode( 'bartag', 'bartag_func' );
  

Just a couple of extra notes

• For some reason I can’t see why you would need the global $post. It seems totally unnecessary from looking at your code

• Also, you have cat in your attributes that does not get used.

EDIT

It seems that your custom field holds more than one value. The best way forward here will be to do a var_dump() of your custom field to see what data is returned and what the exact format is of it.

Check this post I have recently done on custom fields