Creditably is how you do something when the result deserves praise. She sang creditably. They played creditably against a stronger team. It means well enough that people can fairly say well done — not in a way that uses a credit card, and not in a believable way. Same feeling as creditable: polite, a bit formal, often used when the person did not win but did not embarrass themselves either. You will hear it from teachers and commentators more than from friends chatting.