Element none used (4)
I believe the answer is:
neon
'element' is the definition.
(I know that neon is a type of element)
'none used' is the wordplay.
'used' indicates anagramming the letters.
'none' anagrammed gives 'NEON'.
(Other definitions for neon that I've seen before include "Type of lighting" , "Gas used in fluorescent lamps" , "Small plant; colour" , "Form of lighting" , "Noble gas used in illuminated signs" .)