To perpetrate only evil will not help one at all

I think it could be either:

Which length description are you looking for?:

2,2,4

do no good

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'to perpetrate only evil will not' is the definition.
I know nothing about this answer so I can't judge whether this works.

'help one at all' is the wordplay.
I cannot really understand how this works, but
'at' could be 'on' (location) and 'on' is present in the answer.
'help' could be 'dogood' (doing good is a kind of helping) and 'dogood' is located in the leftover letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).

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