No term for mediocrity or stupidity? (6)

I believe the answer is:

idiocy

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'stupidity?' is the definition.
(idiocy is a kind of stupidity)

I can't explain the remainder of the clue.

(Other definitions for idiocy that I've seen before include "Great folly" , "Foolish action or behaviour" , "Stupid behaviour or talk" , "Extreme foolishness" , "Foolish act" .)

I've seen this clue in The Irish Times and the Irish Times (Crosaire).

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