Cut the zest from the orange, omitting the white pith, and slice finely. Squeeze the orange for juice. Combine sugar, star anise, cloves, orange zest and orange juice into a deep saucepan. Add water and bring to the boil until sugar dissolves completely.
Add the pears and pour in Cointreau. Make sure that the pears are submerged in the liquid (if there is not enough water, add some more).
Reduce the heat and simmer pears for 20-25 minutes or until they are almost tender.
Drain the pears from the liquid and leave to cool completely. Chill the pears in the refrigerator for at least 1 hour before serving.