Sometimes heartless form of address (5)

I believe the answer is:

madam

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'form of address' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for madam that I've seen before include "precocious schoolgirl?" , "Formal address to a woman - precocious little girl" , "Woman of standing" , "Make wildly happy" , "Woman with status - girl with bad manners" .)

I've seen this clue in the Evening Standard.

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