The crystal structure of a disordered form of Cr1/3NbS2 has been characterized using diffraction and inelastic scattering of synchrotron radiation. In contrast to the previously reported symmetry (P6322), the crystal can be described by a regular twinning of an average P63 structure with three disordered positions of the Cr ions. Short-range correlations of the occupational disorder result in a quite intense and structured diffuse scattering; a static nature of the disorder was unambiguously attributed by the inelastic x-ray scattering. The diffuse scattering has been modeled using a reverse Monte-Carlo algorithm assuming a disorder of the Cr sublattice only. The observed correlated disorder of the Cr sublattice reduces the temperature of the magnetic ordering from 130 to 88 K and drastically modifies the field dependence of the magnetization as it is evidenced by the SQUID magnetometery. We conclude that, in contrast to the magnetic properties assumed for a helicoidal spin structure, the compound under study (which has the same chemical composition and an average structure very close to previous reports) shows the response of a ferromagnetically ordered anisotropic material.