A method and apparatus for clearing a part of a sidelink grant in a wireless communication system is provided. A first wireless device reserves a set of resources comprising at least a first resource and a second resource for sidelink transmission to a second wireless device, and receives, from a third wireless device, sidelink control information (SCI) which schedules sidelink transmission from the third wireless device. When (i) priority of the sidelink transmission from the third wireless device is higher than priority of the sidelink transmission to the second wireless device, (ii) reference signal received power (RSRP) measurement for the received SCI is higher than a threshold, and (iii) a resource for the sidelink transmission from the third wireless device overlaps with the first resource, the first wireless device clears the first resource from the set of resources, and adds a third resource to the set of resources.