Compounds idiot considers great (8)

I believe the answer is:

nitrates

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

'compounds idiot' is the definition.
'nitrates' can be an answer for 'compounds' (I've seen this before). I'm unsure of the 'idiot' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for nitrates that I've seen before include "Fertiliser salts found in train set" , "Compounds" .)

I've seen this clue in The Guardian.

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