Probity not altogether necessary in valedictory notice (4)

I believe the answer is:

obit

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'necessary in valedictory notice' is the definition.
'obit' can be an answer for 'notice' (I've seen this before). I'm not sure about the 'necessary in valedictory' bit.

'probity not altogether' is the wordplay.
'not altogether' says the answer is hidden in the clue (some but not all of the letters in the clue).
'OBIT' is hidden within 'probity'.

Can you help me to learn more?

(Other definitions for obit that I've seen before include "provides announcement of death" , "Death notice (colloq.)" , "Passing information" , "Notice of one's passing" , "passing mention" .)

I've seen this clue in The Guardian.

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