Mercy for only one in four (7)

I believe the answer is:

quarter

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'mercy' is the definition.
(I know that quarter is a type of mercy)

I don't understand the remainder of the clue.

(Other definitions for quarter that I've seen before include "A fourth - city district" , "Area of town; mercy" , "Divide into four" , "deadly action after draw?" , "three months" .)

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

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