Element hard: gone dry perhaps (8)
I believe the answer is:
hydrogen
'element' is the definition.
(I know that hydrogen is a type of non-metal)
'hard gone dry perhaps' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'perhaps' is an anagram indicator.
'gone'+'dry'='gonedry'
'gonedry' anagrammed gives 'ydrogen'.
'h'+'ydrogen'='HYDROGEN'
(Other definitions for hydrogen that I've seen before include "Lightest gas" , "Most abundant element - gas - H" , "Gas, symbol H" , "Lightest of all elements" , "Ubiquitous gas" .)