It's helpful to carry out a successful revolution (2,1,4,4)

I believe the answer is:

do a good turn

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'successful revolution' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'it's helpful to carry out a' is the wordplay.
'it's helpful' becomes 'goodturn' (I can't justify this - if you can you should believe this answer much more).
'to' says to put letters next to each other (I've seen this in other clues).
'carry out' becomes 'do' (synonyms).
'do'+'a'='doa'
'goodturn' put after 'doa' is 'DO A GOOD TURN'.

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

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