An element of jazz in classical music (4)
I believe the answer is:
zinc
'an element' is the definition.
(I know that zinc is a type of metal)
'of jazz in classical music' is the wordplay.
'of' says the answer is hidden in the clue.
'ZINC' is hidden within 'jazz in classical music'.
(Other definitions for zinc that I've seen before include "It is used to coat iron against corrosion" , "Blusish-white lustrous metallic element" , "Blue-white metallic element, atomic number 30" , "Penultimate element (alpha. order)" , "Metal alloyed with copper to make brass" .)