Something of jazz included in metal? (4)
I believe the answer is:
zinc
'metal?' is the definition.
(zinc is a kind of metal)
'something of jazz included in' is the wordplay.
'something of' indicates a hidden word (I've seen 'something' mean this (I've seen this in other clues)).
'ZINC' is hidden in the letters of 'jazz included in'.
(Other definitions for zinc that I've seen before include "Blusish-white lustrous metallic element" , "Silvery-white metal" , "Bluish-white lustrous metallic element" , "Anti-corrosion agent" , "Metallic element present with copper in brass" .)