Pen-mark on an execution warrant? (5-6)

I believe the answer is:

death-stroke

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'pen-mark' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'on an execution warrant?' is the wordplay.
'on' is a charade indicator (letters next to each other).
'an execution' becomes 'stroke' (I can't justify this - if you can you should believe this answer much more).
'warrant?' becomes 'death' (death warrant is a kind of warrant).
'stroke' put after 'death' is 'DEATH-STROKE'.

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I've seen this clue in The Irish News.

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