The time dependence of scattered light intensity measured in transmitted mode in relaxer 8/65/35 PLZT ceramics under the action of rectangular pulses of electric field were analyzed as a result of evolution of the heterophase structure containing the polar clusters in paraphase matrix. The scenario of the relaxer phase evolution near transition to ferroelectric phase was extracted from the peculiarities of "switching" and spontaneous "backswitching" kinetics investigated in details.