Instruments musician initially on island played (9)
'instruments' is the definition.
(mandolin is a kind of instrument)
'musician initially on island played' is the wordplay.
'initially' says to take the initial letters.
'played' indicates an anagram.
The initial letter of 'musician' is 'm'.
'onisland' anagrammed gives 'andolins'.
(Another definition for mandolins that I've seen is "instruments".)