The necessary state to turn lead to tungsten (5)
I believe the answer is:
wonga
'the necessary' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'state to turn lead to tungsten' is the wordplay.
'state' becomes 'GA' (abbreviation for the US state).
'to' says to put letters next to each other (I've seen this in other clues).
'turn lead' becomes 'on' (I can't justify this - if you can you should believe this answer much more).
'to' means one lot of letters go next to another (I've seen this in other clues).
'tungsten' becomes 'W' (W is the chemical symbol for tungsten).
'on' put after 'w' is 'won'.
'ga' after 'won' is 'WONGA'.
Can you help me to learn more?
(Other definitions for wonga that I've seen before include "Money (sl.)" , "Dosh (informal)" , "Money (slang)" , "Money (informal)" , "Be sick" .)