The aim of this work is to improve the secrecy capacity of primary users (PUs), meanwhile, spectrum utilisation and energy efficiency are considered. the authors present a communication system model with secondary users (SUs). The SUs are provided access to the spectrum. Also, by means of beamforming, their signals will not interfere the PUs but eavesdropper, and the PUs' transmissions are protected. By leveraging the SUs instead of traditional jamming nodes can also make the energy efficiency higher. They formulate the system model, signalling plan, and key enabling techniques to enhance the spectrum efficiency and PUs' physical-layer security with SUs' participation. They provide theoretic analysis of a sum capacity maximisation under a certain power constraint to evaluate the performance of this system. Numerical results show that the proposed scheme not only improves PU's secrecy capacity but also enhances the spectrum utilisation.