We investigate a Fe-2 molecular nanomagnet that displays a giant, field-induced step in its magnetisation curve. Detailed magnetisation and magnetic torque investigations demonstrate that in this Fe-2 system the single-ion anisotropy is dominant over the isotropic exchange coupling. Accurate spin Hamiltonian parameter values and tensor orientations are obtained. The theoretical analysis reveals that this system is a very promising candidate for the direct observation of the Neel vector tunnel splitting in weakly coupled molecular nanomagnets. Copyright (C) EPLA, 2011