Elementary sum I do get wrong (6)

I believe the answer is:

sodium

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'elementary sum i do get wrong' is the definition.
I can't judge whether this definition defines the answer.

'sum i do get wrong' is the wordplay.
'get wrong' indicates an anagram (I've seen 'got wrong' mean this).
'sum'+'i'+'do'='sumido'
'sumido' with letters rearranged gives 'SODIUM'.

Can you help me to learn more?

(Other definitions for sodium that I've seen before include "Metal present in common salt" , "Element discovered by Humphry Davy" , "1 down, symbol Na" , "Chemical in salt" , "... is its atomic number: symbol Na" .)

I've seen this clue in The Globe and Mail.

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