Planned second chemistry edition (7)

I believe the answer is:

schemed

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'planned' is the definition.
(scheming is a kind of planning)

'second chemistry edition' is the wordplay.
'second' becomes 's' (common abbreviation).
'chemistry' becomes 'chem' (I am not sure about this - if you are sure you should believe this answer much more).
'edition' becomes 'ed' (abbreviation).
's'+'chem'+'ed'='SCHEMED'

Can you help me to learn more?

(Other definitions for schemed that I've seen before include "Devised plans" , "Plotted and planned" , "Cooked up" , "Secretly plotted" , "contrived" .)

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

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