Release not charged (4)

I believe the answer is:

free

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'release' is the definition.
(I know that release can be written as free)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for free that I've seen before include "Type of tenure" , "Allowed to do as one pleases" , "On the house" , "Unconfined" , "nought" .)

I've seen this clue in The Irish News.

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