What dead men do on being held up by informers (4,2,5)

I believe the answer is:

tell no tales

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'what dead men do' is the definition.
I know nothing about this answer so I can't judge whether this works.

'on being held up by informers' is the wordplay.
'on' indicates putting letters inside (as in clothing 'on' a person).
'being held up by' becomes 'no' (I can't justify this - if you can you should believe this answer much more).
'informers' becomes 'tell tales' (I've seen this in another clue).
'no' placed within 'telltales' is 'TELL NO TALES'.

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I've seen this clue in The Globe and Mail.

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