Matter concealed by magistrate (4)

I believe the answer is:

gist

'matter' is the definition.

'concealed by magistrate' is the wordplay.
'concealed' says the answer is hidden in the clue.
'GIST' is hidden within 'by magistrate'.

(Other definitions for gist that I've seen before include "The substance of a text" , "Meat" , "Essential point or meaning of, say, the matter" , "Substance or general idea" , "Central idea" .)

I've seen this clue in The Everyman puzzle in The Observer.

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