Standing Hip Abduction
This exercise can be important for balance on the standing leg, whilst also targeting important muscles around the hip on the moving leg.
Physio
Stand tall holding the edge of a surface or putting your hands on the wall. Ensuring your feet face forwards, take one leg out to the side as far as it can go without bending your body to the side or hitching through your hip. Then return it back to the standing position. Repeat this for the desired number of repetitions. To make this harder, try using a looped resistance band.