Post-war churches retaining an opportunity of success, given effort (8,6)

I believe the answer is:

fighting chance

'opportunity of success given effort' is the definition.
(a chance to succeed if effort is made)

I don't understand the rest of the clue.

(Other definitions for fighting chance that I've seen before include "Decent prospect" , "A possibility of success if great effort is made" , "reasonable prospect" , "provided by Tweedledum's rattle?" , "Potential for success" .)

I've seen this clue in The Times.

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