American evergreen tree that produces round gourds? A fungus that lives within a plant? The twelve Apostles chosen by Christ to preach his gospel? A stringed instrument that produces a musical sound when a current of air passes over the strings? Small New World monkey with long hair and bushy tail?
The stringed instrument is an aeolian harp.
It would be helpful if you could give the number of letters in the clues and any known letters that you already have