wp_get_split_term()

wp_get_split_term( int $old_term_id, string $taxonomy ): int|false

function wp_get_split_term( $old_term_id, $taxonomy ) {
	$split_terms = wp_get_split_terms( $old_term_id );

	$term_id = false;
	if ( isset( $split_terms[ $taxonomy ] ) ) {
		$term_id = (int) $split_terms[ $taxonomy ];
	}

	return $term_id;
}