Melianthus have their top growth killed in winter in cold areas but where you are you are probably more likely to get wind damage so this simply needs clearing away in spring. In milder areas, where the top growth remains intact, cut this back during early spring to within two or three buds from the base. Don't forget to wear gloves and long-sleeves to protect hands and arms from the irritant sap. Wrong time of year for Oz but put it in your diary.