Keenness of a conspiracy case to accept civil action after start (6)

I believe the answer is:

acuity

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'keenness' is the definition.
(synonyms)

I can't explain the remainder of the clue.

(Other definitions for acuity that I've seen before include "Showing ingenuity" , "Sharp-sightedness, keenness" , "Sharpness of mind, keenness" , "Sharpness (e.g. of mind)" , "Quick and penetrating intelligence" .)

I've seen this clue in the Sydney Morning Herald.

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