Part of a guitar
I believe the answer is:
fret
'part of a guitar' is the definition.
(I know this)
This is the entire clue.
(Other definitions for fret that I've seen before include "Worry - ridge on guitar's fingerboard" , "Harry - on the guitar" , "Worry - bar on the fingerboard of a stringed instrument" , "Be anxious -- part of a fingerboard" , "ridge > that obscures sea view" .)