Answer:

dauphin

AnswerCrossword Clue
DAUPHINEldest son of a French king
DAUPHINKing's eldest son, in old France
DAUPHINLe roi's heir, perhaps
DAUPHINKing's eldest, in old France
DAUPHINFrench king's eldest son
DAUPHINFrench title.
DAUPHINPrincely French name: 1349-1830
DAUPHINRoyal French title
DAUPHINHeir apparent to a French king
DAUPHINCharles V, when his father became king of France