Mandolin's kin (4)
I believe the answer is:
lute
'mandolin's kin' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lute that I've seen before include "Old stringed instrument with a pear-shaped body" , "Old guitar-like instrument played by minstrels" , "Plucked, pear-shaped instrument" , "Ancient stringed instrument" , "Stringed instrument shaped like a halved egg" .)