Non-metallic element (6)
(Other definitions for sulphur that I've seen before include "Element, atomic no. 16" , "Chemical used in match heads" , "Yellow non-metallic element" , "S (chem.)" , "Chemical element" .)
(Other definitions for silicon that I've seen before include "Chip substrate element" , "Element used in integrated circuits" , "Computer chip element" , "Element used in making electronic chips" , "Element occurring in sand" .)
'non-metallic element' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for boron that I've seen before include "element needed for steel" , "component of steel" , "Chemical element, symbol B" , "Non-metallic element, symbol B" , "Atomic no 5" .)
(Other definitions for iodine that I've seen before include "Black/violet element" , "Tincture for cuts" , "Mild antiseptic" , "Dark-violet antiseptic" , "Hanging tuft" .)
'non-metallic element' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for carbon that I've seen before include "Dioxide or monoxide, say" , "Element in soot, charcoal, etc" , "Element of which diamonds are formed" , "Common element" , "This paper is used to make copies" .)