Off and on, courage soon exposes instrument of thought (7)

I believe the answer is:

organon

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'instrument of thought' is the definition.
(I've seen this in another clue)

'off and on courage soon' is the wordplay.
'off and on' indicates alternate letters (letters used at regular intervals).
'soon' becomes 'anon' (synonyms).
The alternate letters of 'courage' are 'org'.
'org'+'anon'='ORGANON'

'exposes' is the link.
I am not very happy about this link. It may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for organon that I've seen before include "Set of principles" , "system of logic" , "system for acquiring knowledge" .)

I've seen this clue in The Independent.

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