Mandolin's cousin (4)
I believe the answer is:
lute
'mandolin's cousin' 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 "Plucked, pear-shaped instrument" , "Old plucked instrument" , "Elizabethan stringed instrument" , "Stringed instrument shaped like a halved egg" , "Protective packing" .)