Smashing atoms up is to create element (9)
I believe the answer is:
potassium
'element' is the definition.
(potassium is a kind of element)
'smashing atoms up is' is the wordplay.
'smashing' is an anagram indicator.
'atoms'+'up'+'is'='atomsupis'
'atomsupis' anagrammed gives 'POTASSIUM'.
'to create' is the link.
(Other definitions for potassium that I've seen before include "... is its atomic number: symbol K" , "Soft metal, symbol K" , "Soft reactive metal" , "Element K" , "Silvery metallic element" .)