In heartless prison, I lowered blind (8)

I believe the answer is:

jalousie

'blind' is the definition.
(I know that jalousie is a type of shutter)

I can't explain the remainder of the clue.

(Other definitions for jalousie that I've seen before include "Slatted blind or shutter" , "Louvred window" .)

I've seen this clue in The Guardian.

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