Key management has remained a difficult issue in wireless device networks (WSNs) as a result of the constraints of device node resources. Various key management schemes that trade off security and operational necessities are proposed in recent years. Wireless device Networks (WSNs) comprises tiny sensor nodes with strained energy, memory and computation capabilities. Sensors can also be embedded into wearable devices to track vital signs of patients in healthcare domain. Mobility of sensor devices as per the demands of the application makes WSNs dynamic. Addressing key security requirements such as node authentication, data integrity and confidentiality is crucial for the success of critical WSN applications.In this paper, we propose a certificate less-effective key management (CL-EKM) protocol for secure communication in dynamic WSNs characterized by node mobility. The CL-EKM supports efficient key updates when a node leaves or joins a cluster and ensures forward and backward key secrecy. The protocol also supports efficient key revocation for compromised nodes and minimizes the impact of a node compromise on the security of other communication links. A security analysis of our scheme shows that our protocol is effective in defending against various attacks.