Unit of heredity a woman talked of (4)

I believe the answer is:

gene

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'unit of heredity' is the definition.
(I've seen this in another clue)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for gene that I've seen before include "Bodily factor controlling heredity" , "Unit of heredity significance" , "Biological factor determining heredity" , "and 16 Down: Rockabilly singer" , "-- Pitney, singer" .)

I've seen this clue in The Times.

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