Listening intently – debt's twice changed hands (3,4)

I believe the answer is:

all ears

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'listening intently' is the definition.
(I've seen this in another clue)

I don't understand the remainder of the clue.

(Other definitions for all ears that I've seen before include "Prepared to listen" , "description of cornfield?" , "Listening attentively" , "Being very attentive" , "Very alert" .)

I've seen this clue in The Guardian.

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