Experimental writing (5)

I believe the answer is:

essay

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'writing' is the definition.
(I know that essay is a type of writing)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for essay that I've seen before include "Make an effort or attempt" , "Make an effort to write one" , "Analytic or interpretive literary composition (5_" , "Old experiment" , "Try; dissertation" .)

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

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