Free? Anything but (9)

I believe the answer is:

priceless

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'free?' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I don't see?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for priceless that I've seen before include "Very precious; highly amusing" , "Of inestimable value" , "Of incalculable value" , "Very precious; absurd" , "Extremely precious" .)

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

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