George's half-rational regarding Earth studies (10)

I believe the answer is:

geological

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'george's half-rational regarding earth studies' is the definition.
I can't judge whether this defines the answer.

'george's half-rational' is the wordplay.
'half' means to take half the letters.
'rational' becomes 'logical' (similar in meaning).
'george' halved is 'geo'.
'geo'+'logical'='GEOLOGICAL'

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(Other definitions for geological that I've seen before include "about the structure of the earth" , "earth science" .)

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

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