To an American it sounds easy — I am returning sweetcorn (5)

I believe the answer is:

maize

I'm a little stuck... Click here to teach me more about this clue!

'sweetcorn' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for maize that I've seen before include "Source of sweetcorn" , "Source of oil" , "Sweet corn" , "plant with ears" , "one could make a meal of it" .)

I've seen this clue in The Guardian.

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