Peel and finely chop the onion. Mix yoghurt, salad cream and onion. Season with salt and pepper. Chop the nuts. Squeeze 2 clementines. Peel 3 clementines and divide into slices.
Peel and wash the celery and slice into thin sticks. Wash apples, cut into quarters, remove seeds and slice into thin sticks. Mix both immediately with clementine juice. Fold in yoghurt sauce, clementines and nuts.
Let the salad stand for at least 30 minutes. Season with salt, pepper, lemon juice and 1 pinch of sugar.