Move only if mouse click the Terrain

I want to move the player only if mouse click on Terrain, any idea?

         // Moves the Player if the Left Mouse Button was clicked
         if (Input.GetMouseButtonDown (0) && GUIUtility.hotControl == 0) {
             
                         Plane playerPlane = new Plane (Vector3.up, myTransform.position);
                         Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
                         float hitdist = 0.0f;
             
                         if (playerPlane.Raycast (ray, out hitdist)) {
                                 Vector3 targetPoint = ray.GetPoint (hitdist);
                                 destinationPosition = ray.GetPoint (hitdist);