One element that may be split into many (8)
I believe the answer is:
antimony
'one element' is the definition.
(antimony is a kind of element)
'split into many' is the wordplay.
'split' indicates anagramming the letters.
'into'+'many'='intomany'
'intomany' with letters rearranged gives 'ANTIMONY'.
'that may be' is the link.
(Other definitions for antimony that I've seen before include "One element" , "My nation (anag) - metallic element" , "Bluish-white element, symbol Sb" , "Toxic metallic element used in semiconductors" , "Brittle element" .)