Crossword Genius

Currency left after rest damaged in battering (5,8)

Ross

I believe the answer is:

pound sterling

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'damaged in battering' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.

'currency left after rest' is the wordplay.
'currency' becomes 'pound' (I have seen 'Egyptian currency ' mean 'pound' so perhaps 'currency' could also mean 'pound').
'left after rest' becomes 'sterling' (I can't justify this - if you can you should give a lot more credence to this answer).
'pound'+'sterling'='POUND STERLING'

Can you help me to learn more?

(Other definitions for pound sterling that I've seen before include "Tender" , "UK currency" .)

I've seen this clue in The Independent.
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