Nip up to fasten (3)

I believe the answer is:

'fasten' is the definition.
(I know this)

'nip up' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'nip' back-to-front is 'PIN'.

'to' is the link.

(Other definitions for pin that I've seen before include "Initially, confidential number for use of bank card" , "Small object to fasten or attach" , "Hold (down)" , "Fastener; brooch" , "Debit-card number" .)

I've seen this clue in the Sydney Morning Herald.

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