If clementines are unavailable, substitute 1/3 cup freshly squeezed juice and a little zest from a navel orange.
In a blender, combine the shallot, mustard, salt, and clementine juice and blend until smooth. Set aside. Steam the beans until bright green and barely tender, about 6 minutes. Transfer to a large bowl and drizzle with the citrus dressing. Top with the pecans and clementine zest to taste and serve.