A lightweight-construction fastener (10) having a one-piece clip body (20) made of plastic and a clip nut (40). The clip body has the basic shape of a clamp, having two opposite legs (22, 24) extending in the longitudinal direction and a cage (28) in which the clip nut is floatingly mounted. The clip nut in turn has a nut base (42) which is substantially planar. A main part (44) is structured on the nut base and has a cover surface (41) and a plurality of side walls (51, 51′) which extend between the nut base and the cover surface. The side walls of the main part preferably have a convex curvature and the cage has correspondingly designed concave walls. The sizing is such that the convex-concave surface pairs act as torque supports during use of the lightweight-construction fastener.