This paper reports an FPGA-based P4-enabled Smart NIC solution which is designed and implemented for webscale cloud and to meet 5G/Beyond 5G networking requirements. The P4-enabled Smart NIC solution leverages the open standards, platforms and software-defined approaches, responds to the real time Data Centre Networking service requests, in particularly, enables the end-to-end network slicing, which is one of the critical requirements of multi-tenancy 5G network. We discussed the possibilities and challenges of P4 specification implementation in the FPGA to realise the Smart NIC functionalities. And after that, we showed its data plane programmability and flexibility with P4 features. Furthermore, we demonstrated its application scenario in an 5G environment mainly focusing on edge Data Centre to core Data Centre network slicing. The setup interconnects the P4enabled Smart NIC with optical Bandwidth Variable Transponders, and the system offers agile 100Gbps interface to transport the packets through P4-defined data plane for L2/L3/L4 parsing and action. The P4-enabled Smart NIC can change the data plane pipelines in seconds, and it can achieve maximum 84.8Gbps throughput. With P4 programmed hardware offloaded Segment Routing can produce 30% more bandwidth than without.