Coin once used in City University (3)

I believe the answer is:

ecu

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'coin once' is the definition.
The definition suggests a singular noun which matches the answer.

'city university' is the wordplay.
'city' becomes 'ec' (the City of London postcode).
'university' becomes 'U' (abbreviation for university).
'ec'+'u'='ECU'

'used in' acts as a link.

Can you help me to learn more?

(Other definitions for ecu that I've seen before include "The euro's predecessor" , "Former term for Euro" , "Original name of euro" , "Old European currency unit" , "Former European currency" .)

I've seen this clue in The Times.

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