Poetry without rules costs nothing (4,5)

I believe the answer is:

free verse

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'poetry' is the definition.
(I have seen 'Unconventional poetry ' mean 'free verse' so perhaps 'poetry' could also mean 'free verse')

I can't explain the rest of the clue.

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(Other definitions for free verse that I've seen before include "Ref severe on flowing poetry" , "Poetry without regular metre or rhyme" , "Unconventional poetry" , "irregular lines" .)

I've seen this clue in The Irish News.

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