The pick of stringed instruments? (8)
I believe the answer is:
plectrum
'the pick' is the definition.
(a guitar pick)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for plectrum that I've seen before include "Implement for plucking guitar strings" , "Guitar pick" , "Object used to pluck stringed instrument" , "Small piece of plastic for plucking musical strings" , "Guitarist's aid" .)