Heat oven to 200C/180C fan/gas 6. Pat the duck legs dry with kitchen paper and rub in the five-spice and some seasoning. Pour the vinegar, soy and orange juice into a small roasting tin and put the duck on top. Cover with foil and cook for 30 mins, then remove the foil and increase oven to 240C/220C fan/ gas 9, or put under the grill and cook until the skin is crisp. Remove and strain the liquid through a sieve. Let the duck cool until you can shred the meat from the bones. Skim fat from the liquid.
Meanwhile, gently toss together the oranges, watercress, radishes, chicory and spring onions. Pour over reserved cooking liquid, then add the duck and arrange on a platter.