A wok that doesn't rock is useful for deep-oil frying, because it gets ever wider going from bottom to top. So long as you don't overfill it (say, no more than 1/3 of its depth, but you can increase this with experience to maybe 1/2), the displacement of oil as you add the bhajis will be absorbed by the additional volume available at the top of the wok into which the oil is displaced. And if it does overflow and catch fire, don't panic : just turn off the heat, cover it with a wok lid, and the flames will eventually go out. In no circumstances try to carry a flaming wok (or any other flaming cooking utensil) outside : horrible horrible accidents can occur if you try.