  FeVO$_4$ has been studied by heat capacity, magnetic susceptibility, electric
polarization and single crystal neutron diffraction experiments. The triclinic
crystal structure is made of \emph{S}-shaped clusters of six Fe$^{3+}$ ions,
linked by VO$_4^{3-}$ groups. Two long-range magnetic ordering transitions
occur at T$_{N1}$=22K and T$_{N2}$=15K. Both magnetic structures are
incommensurate. That stable below T$_{N1}$ is collinear with amplitude
modulated moments whereas below T$_{N2}$ the arrangement is non-collinear with
a helicoidal modulation. Below T$_{N2}$, \fevo becomes weakly ferroelectric
coincidentally with the loss of the collinearity of the magnetic structure. We
conclude that \fevo provides another example of frustrated spiral magnet
similar to the classical TbMnO$_3$ compound. However, \fevo has quenched
orbital moments and a particular structure clarifying the respective role of
anisotropy and magnetic frustration in this type of multiferroic materials.
