// GeneratePress Search Box Clear

by 
add_filter( 'generate_navigation_search_output', 'tu_remove_search_query' );
function tu_remove_search_query() {
  printf( // WPCS: XSS ok, sanitization ok.
    '<form method="get" class="search-form navigation-search" action="%1$s">
      <input type="search" class="search-field" value="" name="s" title="%2$s" />
    </form>',
    esc_url( home_url( '/' ) ),
    esc_attr_x( 'Search', 'label', 'generatepress' )
  );
}