Central fund issues currency when confidence is lacking (6)

I believe the answer is:

unsure

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'when confidence is lacking' is the definition.

'central fund issues currency' is the wordplay.
'central' indicates the central letters.
'issues currency' becomes 'sure' (I can't explain this - if you can you should give a lot more credence to this answer).
The middle letters of 'fund' are 'un'.
'un'+'sure'='UNSURE'

Can you help me to learn more?

(Other definitions for unsure that I've seen before include "Far from certain" , "Not certain, undecided" , "regarded as somewhat precarious" , "Not certain or confident" , "Not certain, dubious" .)

I've seen this clue in The Guardian.

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