Insane game getting rid of one disruptive element (9)
I believe the answer is:
manganese
'element' is the definition.
(manganese is a chemical element)
'insane game getting rid of one disruptive' is the wordplay.
'getting rid of' is a deletion indicator.
'one' becomes 'I' (Roman numeral).
'disruptive' indicates anagramming the letters.
'insane'+'game'='insanegame'
'insanegame' with 'i' taken out is 'nsanegame'.
'nsanegame' anagrammed gives 'MANGANESE'.
(Other definitions for manganese that I've seen before include "Element - Anne's game (anag)" , "Metallic element used in steels" , "Element, symbol Mn" , "Metal used in some steels" , "Metal used in steel making" .)