Church distant from fences in part of East Anglia (4)

I believe the answer is:

fens

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'fences in part of east anglia' is the definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for fens that I've seen before include "marshland" , "East Anglian marshes" , "Marshy eastern England region" , "Low-lying wetlands" .)

I've seen this clue in The Mirror.

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