Over the past decade, the Internet of Things (IoT) has attracted enormous interest from the research community and industry. IoT requires a synergy of various technologies, and Wireless Sensor Networks (WSNs) are poised to play a critical role in many IoT applications like weather monitoring, smart-grid, smart-city, etc. Synchronization of local clocks of the WSN nodes is essential in many network functionalities and thus a time synchronization protocol is required in WSNs. Although several synchronization protocols have been proposed for WSNs, most of them are simulation-based works. They make many assumptions at a high abstraction level and do not take into account the conditions of the Line-of-Sight (LOS) in the network. These factors significantly affect the performance of these protocols. Thus, conclusive experimental proof of the effectiveness of these protocols for different LOS conditions is required. In this direction, this work proposes a time synchronization protocol called Efficient and Simple Algorithm for Time Synchronization (E-SATS) for a cluster-based WSN. E-SATS has been tested on a large-sized WSN testbed in different LOS scenarios in this work and compared with the existing state-of-the-art protocols. E-SATS outperformed existing protocols by achieving up to 6 times better accuracy as compared to existing protocols with significantly lesser computations and energy consumption.