French sister claims some land adjoining Catholic church (5,5)

I believe the answer is:

sacre coeur

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'church' is the definition.
Both the answer and definition are singular nouns.
Maybe there's a link between them I don't understand?

'french sister claims some land adjoining catholic' is the wordplay.
'french sister' becomes 'soeur' (I've seen this in another clue).
'claims' indicates putting letters inside.
'some land' becomes 'acre' (unit of land).
'adjoining' says to put letters next to each other.
'catholic' becomes 'C' (abbreviation as in RC for Roman Catholic).
'acre'+'c'='acrec'
'soeur' placed around 'acrec' is 'SACRE-COEUR'.

Can you help me to learn more?

(Another definition for sacre coeur that I've seen is " Paris landmark".)

I've seen this clue in The Independent.

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