The banknote makers' union (4)

I believe the answer is:

knot

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'makers' union' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

'the banknote' is the wordplay.
'KNOT' is hidden in amongst the letters.
However, I am not sure how this is indicated.

Can you help me to learn more?

(Other definitions for knot that I've seen before include "Tie; sandpiper" , "Fastening; sea bird" , "bond, perhaps?" , "Tight cluster (of people)" , "Hard round cross-grained piece in wood" .)

I've seen this clue in the Evening Standard.

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