Help about element helium separation (9)
I believe the answer is:
apartheid
'separation' is the definition.
(historical policy of segregation in South Africa)
'help about element helium' is the wordplay.
'help' becomes 'aid' (synonyms).
'about' indicates putting letters inside.
'element' becomes 'part' (a segment or piece).
'helium' becomes 'he' (chemical symbol).
'part'+'he'='parthe'
'aid' enclosing 'parthe' is 'APARTHEID'.
(Other definitions for apartheid that I've seen before include "enforced separation" , "System of segregation formerly practised in South Africa" , "Social policy of racial segregation" , "divisive policy" , "Tyrannical system in S Africa now abandoned" .)