Possible Clues:

• Flipping big herb is cooked for cobblers
• Double Dutch
• Gobbledegook
• Reversed major error bringing in monarch's rubbish
• Unintelligible speech
• Big Herb is relaxing in bunk
• Language invented by the Bee Gees?
• Prattle from Big Herb is translated
• Husband and father, born great, overthrown? There's no sense in it
• Moving north, husband and dad start to breed whopping rhubarb