Tamper with setters' exactitude (6)

I believe the answer is:

rigour

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'exactitude' is the definition.
(I have seen 'Strict exactitude' mean 'rigour' so perhaps 'exactitude' could also mean 'rigour')

'tamper with setters'' is the wordplay.
'tamper with' becomes 'rig' (I've seen this in another clue).
'setters'' becomes 'our' (I can't justify this - if you can you should give a lot more credence to this answer).
'rig'+'our'='RIGOUR'

Can you help me to learn more?

(Other definitions for rigour that I've seen before include "Austerity - strictness" , "Strict exactitude" , "Sternness" , "Excessive severity" , "Preciseness - severity" .)

I've seen this clue in The Sun.

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