Possible Clues:

• Poor complain endlessly about king's broadcast
• Trumpet for silent type crossing island
• Declare in favour of petitioner's cause
• Announce that one's no longer an amateur?
• Shout aloud, for I am trapped by shellfish
• Broadcast
• Declare from the pulpit in one of the cathedrals, it's a form of insurance
• Expert given right to shout from the housetops
• Publish demand made by authority
• Shout from the rooftops