Ridge on a guitar's neck (4)
I believe the answer is:
fret
'ridge on a guitar's neck' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for fret that I've seen before include "Fog" , "Chafe, be anxious" , "Worry - pine" , "Worry; wet mist" , "Bar on fingerboard of guitar" .)