Possible Clues:

• Read, as enemy messages
• Fish in river finds crack
• Convert a message into ordinary language
• Work out message in Christmas-time poem
• How to work out there's fish in the river?
• Crack joke during abridged act
• Make last month's poem understandable
• 80-89 perhaps old for one to solve puzzle
• Make sense of a verse for the Christmas period
• Make clear the river is stocked with fish