Metal zither inspired new composer's intros (4)
I believe the answer is:
zinc
'metal' is the definition.
(zinc is a kind of metal)
'zither inspired new composer's intros' is the wordplay.
'intros' says to take the initial letters (I've seen 'intro' mean this).
The first letters of 'zither inspired new composers' is 'ZINC'.
(Other definitions for zinc that I've seen before include "Metal used for galvanising steel" , "It is used to coat iron against corrosion" , "Constituent of brass" , "Ingredient in brass" , "Mineral" .)