Unionised workforce's failure inevitable, according to Spooner (4,5)

I believe the answer is:

shop floor

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

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

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(Other definitions for shop floor that I've seen before include "Workers" , "part of factory" .)

I've seen this clue in The Independent.

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