Fixed part of mechanism wound up (6)

I believe the answer is:

mended

'fixed' is the definition.
('mend' can be a synonym of 'fix')

'part of mechanism wound up' is the wordplay.
'part of' says to take the initial letters (I've seen 'part' mean this).
'wound up' becomes 'ended' (how things 'wind up' is how they end).
The initial letter of 'mechanism' is 'm'.
'm'+'ended'='MENDED'

(Another definition for mended that I've seen is " Repaired, fixed".)

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