Something fishy demanded by the deliverer? (3)
I believe the answer is:
cod
'something fishy' is the definition.
(type of fish)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for cod that I've seen before include "swimmer" , "Initially, pay when you receive the goods" , "Initially, pay when you get the goods" , "Tasty fish or slangy nonsense" , "Hoax (sl.); fish" .)