Complex sentence: The arms show the Saffron Crocus within the walls of the castle intended as an heraldic pun (known as Canting arms)- "Saffron walled-in".
Split into simpler sentences: The arms show the Saffron Crocus within the walls of the castle. They are intended as an heraldic pun (known as Canting arms)- "Saffron walled-in".