Guitarist's accessory (4)
(Other definitions for pick that I've seen before include "option" , "flower" , "Hero of a Dickens novel" , "tool for breaking rocks" , "hacker?" .)
'guitarist's accessory' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for capo that I've seen before include "crime boss" , "Head honcho in Cosa Nostra" , "Movable bridge" , "Mafia boss" , "Mafia chief?" .)