Ukulele ridge (4)
I believe the answer is:
fret
'ukulele ridge' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fret that I've seen before include "Guitar ridge; be anxious" , "Bar on fingerboard of guitar" , "ridge > that obscures sea view" , "Display anxiety" , "Worry; sort of saw" .)