Opening large in church area (7)

I believe the answer is:

chancel

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But I can't explain it at all! Could you help me understand?

(Other definitions for chancel that I've seen before include "Part of church near altar" , "Where to see choir" , "Part of church containing altar" , "what's behind the screen" , "Clergy's area of the church" .)

I've seen this clue in The Sun.

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