We describe here a new mechanism of high-T c (critical temperature) superconductivity. According to our cluster phase transition (CPT) model of spin glass systems, magnetic clusters are present in frustrated magnetic lattices. After giving some details of this model, it is envisaged that in high-T c superconducting cuprate systems, which are magnetically frustrated, these magnetic clusters exist in pairs. The two pair partners are interpenetrating and a spin of one cluster forms a singlet pair with a corresponding spin of the partner cluster. This singlet pairing could occur due to a resonating valence bond (RVB) interaction. The Copper pairs, formed by BCS-Migdal-Eliasberg phonon coupling, interact with the singlet coupled cluster pairs and this interaction is responsible for the T c enhancement and other properties of cuprate superconductors. Consequences of this model and its comparison with other existing theories are also discussed.