How to study a former chemical (7)

I believe the answer is:

examine

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'how to study' is the definition.
(I know that examine is a more specific form of investigate)

'a former chemical' is the wordplay.
'a former' becomes 'ex' (prefix meaning former or onetime).
'chemical' becomes 'amine' (I can't justify this - if you can you should believe this answer much more).
'ex'+'amine'='EXAMINE'

Can you help me to learn more?

(Other definitions for examine that I've seen before include "Inspect; question in court" , "Analyse" , "Test or study carefully" , "Question (a witness)" , "vet" .)

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

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