Pb(NO3)2 (aq) + 4 KOH (aq) + Cl2 (g) → PbO2 (s) + 2 KCl (aq) + 2 KNO3 (aq) + 2 H2O (l)
This is an oxidation-reduction (redox) reaction:
PbII - 2 e- → PbIV (oxidation)
2 Cl0 + 2 e- → 2 Cl-I (reduction)
Pb(NO3)2 is a reducing agent, Cl2 is an oxidizing agent.