The reversible process of field induced evolution of heterophase structure existing in relaxer phase was investigated in (6-8)/65/35 PLZT ceramics by in situ measurement of elastic light scattering data under the action of field pulses. The scenario of evolution of heterophase structure during ''switching'' and ''backswitching'' is discussed. The growth velocity and fractal dimensionality of clusters were obtained by proposed mathematical treatment of experimental data.