Here we report results of the study of bent-core (BC) cybotactic nematic LC by dielectric spectroscopy and electro-optic measurements. In the absence of electric field, this material is uniaxial and exhibits only one relaxation process corresponding to the fluctuations of the polar clusters. The application of the external electric field induces biaxiality and the second relaxation process appears in the dielectric spectra. This is assigned to the collective mode. Possible models for cluster transformation under electric field are discussed.