Random defects destroy long-range phase coherence, and inhibit the metal-insulator transition in the charge density wave (CDW) system 1T-TaS2. Photoelectron spectroscopy with high resolution reveals corresponding changes in the electronic structure. Core level spectra indicate a temperature-dependent limited growth of commensurate CDW domains. Screening by free carriers from the domain boundaries reduces the Coulomb repulsion in the Ta d band by similar to 1/3, compared to pure samples, yielding a finite spectral weight at the Fermi level.