Thought blunder on field should be represented in legal document (10)

I believe the answer is:

cogitation

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'thought blunder on field' is the definition.
'cogitation' can be an answer for 'thought' (thesaurus). I'm unsure of the 'blunder on field' bit.

'should be represented in legal document' is the wordplay.
'should be represented' becomes 'og' (I am not sure about this - if you are sure you should believe this answer much more).
'in' indicates putting letters inside.
'legal document' becomes 'citation' (citation is a kind of legal document).
'og' put into 'citation' is 'COGITATION'.

Can you help me to learn more?

(Another definition for cogitation that I've seen is " Study".)

I've seen this clue in The Independent.

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