Advanced one good reason for sacrifice (4)

I believe the answer is:

lent

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'advanced' is the definition.
(advance can mean to lend)

I don't understand the remainder of the clue.

(Other definitions for lent that I've seen before include "Forty days of fasting" , "Time of fasting" , "Christian penitential period" , "Fast time" , "Loaned; a fast" .)

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

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