Releases United fixtures after noon (6)

I believe the answer is:

unties

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'releases' is the definition.
(releases someone tied up)

'united fixtures after noon' is the wordplay.
'united' becomes 'U' (abbreviation).
'fixtures' becomes 'ties' (I can't justify this - if you can you should give a lot more credence to this answer).
'after' is a charade indicator (letters next to each other).
'noon' becomes 'n' (abbreviation for noon).
'ties' put after 'n' is 'nties'.
'u'+'nties'='UNTIES'

Can you help me to learn more?

(Other definitions for unties that I've seen before include "Undoes, a knot perhaps" , "Loosens laces" , "Opens knot to release" , "Undoes, loosens a knot" .)

I've seen this clue in The Guardian.

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