Abstract—Massive Multiple Input Multiple Output (MIMO) using millimetre wave transmissions received significant attention due to its significance of high data rate. However, achieving energy and spectrum efficient millimetre wave communications is challenging due to the dedicated Radio Frequency (RF) chain. Non-Orthogonal Multiple Access (NOMA) is used in beamspace MIMO (BS MIMO) significantly overcome such challenges. This paper proposes the enhanced approach of beamspace MIMO NOMA using a simple yet effective clustering solution with a C-NOMA throughput optimisation algorithm. This proposal involves the lightweight user clustering, lens antenna, and clustering-based iterative power allocation algorithm to enhance each cluster's spectral and energy efficiency performance. After cluster formation, the throughput optimisation function applies. Iterative power optimisation method is proposed to allocate power to each user in each cluster dynamically. Therefore, compared to recent clustering and NOMA methods, the proposed BS MIMO C-NOMA improves Energy Efficiency (EE) and Spectral Efficiency (SE) with minimum computational overhead. Results demonstrate that high EE and SE, respectively, as compared with the percentage of improvement of 26% and 37% in the existing BS MIMO NOMA and improvement of 16.47 % and 27.72 % in User Clustering based on Channel Gain (UCCG) MIMO NOMA among 50 and 100 users.