Cashed in on currency consuming energy (4)

I believe the answer is:

used

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'cashed' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for used that I've seen before include "No longer new" , "given employment" , "not got directly" , "Hand-me-down" , "Brought into service" .)

I've seen this clue in The Hindu.

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