In the most promising new window materials, the light-blocking property of the state-of-the-art transparent polycrystalline ceramics is still located in the UV range, which undoubtedly limits their applications. Herein, a transparent Y2Zr2O7:Tb (YZO:Tb) ceramic for light-shielding windows was prepared by a solid-state reaction and vacuum sintering method. Two simple and efficient routes, with doping concentrations varying and air-annealing temperatures regulating, were developed for the first time to control the content of defect clusters [TbY4+-O2--TbY4+] and [TbY4+-e•], enabling the optical cutoff waveband of these ceramics spanning from UV and BV to green light. These defect clusters generated from an air-annealing process were proposed for the relevant reaction mechanisms concerning light erasure behavior. The controllably tailoring of optical cutoff wavelength from Tb single-doped YZO ceramics, adjusted by defect clusters, may open a novel door to develop lanthanide-doped transparent ceramics for wide-range tunable light-shielding windows.