Metal making gent nuts (8)
I believe the answer is:
tungsten
'metal' is the definition.
(I know that tungsten is a type of metal)
'making gent nuts' is the wordplay.
'making' indicates an anagram.
'gent'+'nuts'='gentnuts'
'gentnuts' is an anagram of 'TUNGSTEN'.
(Other definitions for tungsten that I've seen before include "Wolfram" , "Element used in steels" , "Light-filament element" , "Greyish-white metal used in lamp filaments" , "Hard metal used in light bulb filaments" .)