This paper proposes an enhanced licensed-assisted-access (eLAA) and WiFi coexistence mechanism for LTE deployment in the unlicensed spectrum. Specifically, we utilize the Clear-to-Send-to-Self (CTS-to-Self) frame to seamlessly embed the eLAA transmission within the WiFi access protocol. Unlike traditional LAA ideas, our proposed eLAA is non-intrusive to WiFi users and beneficial to both eLAA and WiFi users. To fully consider the performance of WiFi users, we propose to insert the CTS-to-Self frame under the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism. For further throughput enhancement, we adopt the Nash bargaining solution (NBS) to develop a fair and optimal unlicensed resource allocation scheme and also develop a low computational complexity algorithm to solve the NBS-based problem. Our numerical results corroborate the analytical results and demonstrate the strength of the proposed mechanism.