Possible Clues:

• One next in line for the throne
• Monarch's eldest son, typically
• Such a man is certain to succeed
• Broadcast on the radio by secretary getting back with father of man who'll obviously succeed
• Broadcast on the radio backed public address by the old man to the one who'll obviously succeed
• As eldest child, male, I severely criticise Dad
• He's one to talk over father, being sure of inheritance