The necessity for saving energy, increasing the channel utilisation and security in wireless personal area networks (WPAN) has become crucial, particularly in essential fields like military and medical applications. Thus ZigBee desires an efficient routing protocol to deal with lowest amount of energy expenses and highest network life time. In this paper, ZigBee provides cross layer network protection and application service carried out with hierarchical cluster tree formation. MAC layer utilises the cluster tree formula to establish tree configuration. Subsequently, that cluster table is taken to the routing layer protocol of cross layer ZigBee-based routing protocol (CLZBRP). Here CLZBRP is compared with ad hoc on-demand distance vector routing (AODV) and tree-routing (TR) with QOS. The Sybil attack is encountered by the defense mechanism called random key predistribution technique (I-RKP). It is observed from the experimental result that the proposed approach provides good security against Sybil attack with very high throughput using CLZBRP-I-RKP.