Old Penny's mailed objection (7)

I believe the answer is:

dissent

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'objection' is the definition.
(synonyms)

'old penny's mailed' is the wordplay.
'old penny's' becomes 'dis' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mailed' becomes 'sent' ('send' can be a synonym of 'mail').
'dis'+'sent'='DISSENT'

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(Other definitions for dissent that I've seen before include "Object" , "Disagree" , "Objection" , "Express disagreement" , "Dispute" .)

I've seen this clue in The Sun.

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