Copper loads vegetables (9)

I believe the answer is:

cucumbers

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

'vegetables' is the definition.
(I know this)

'copper loads' is the wordplay.
'copper' becomes 'Cu' (chemical symbol).
'loads' becomes 'cumbers' (I am not sure about this - if you are sure you should believe this answer much more).
'cu'+'cumbers'='CUCUMBERS'

Can you help me to learn more?

(Other definitions for cucumbers that I've seen before include "Cylindrical green fruits" , "Long green fruits" .)

I've seen this clue in the Sydney Morning Herald.

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