Score skin of duck breast and season with salt and pepper.
In a medium-hot ovenproof frying pan, fry duck skin side down for 3-4 minutes to render out fat. Turn and fry for another 2 minutes. Then transfer to preheated oven for 6-7 minutes until cooked to medium.
Take out and rest for 5 minutes.
Place watercress in a bowl with orange segments.
Whisk together all the dressing ingredients. Drizzle over watercress and orange segments.