Remove Parent Theme Action

To remove an action hook you should use the same name, callback and priority used in parent theme. You then need to register it on init like so…

add_action( 'init', 'dna_remove_parent_action');

function dna_remove_parent_action() {

  remove_action( 'dna_header_top', 'dna_add_hamburger', 20 ); 
  
}