Feature of guitar creating worry (4)

I believe the answer is:

fret

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'worry' is the definition.
(to fret about something is to worry)

I cannot understand how the rest of the clue works.

(Other definitions for fret that I've seen before include "Part of a Gibson, say" , "Bar on fingerboard of guitar" , "Harry - on the guitar" , "Worry - bar on the fingerboard of a stringed instrument" , "Split up" .)

I've seen this clue in The Daily Mail.

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