Mother means to hold firm, providing protection for the home (4,6)

I believe the answer is:

damp course

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

(Other definitions for damp course that I've seen before include "Soup?" , "housing benefit?" , "protective component of building" , "Layer of moisture-proof material in a masonry wall" , "feature of building" .)

I've seen this clue in The Independent.

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