Possible Clues:

• A comprehensive case?
• Student's holdall
• Satchel of American visiting Great Britain, going around by train
• Catch fish first and carry home over your shoulder perhaps? That's one for the books!
• Quantity of fish and quantity of game -- youngster may find it a burden
• There's something fishy about that graduate? That a great one for the books!
• A textbook case of fish gathering a singular 1-down?
• Container for primer, perhaps