Chemical element from commercial one put in alcoholic drink (6)
I believe the answer is:
radium
'chemical element' is the definition.
(radium is a kind of chemical element)
'commercial one put in alcoholic drink' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'one' becomes 'i' (Roman numeral).
'put in' indicates putting letters inside.
'alcoholic drink' becomes 'rum' (alcoholic spirit).
'ad'+'i'='adi'
'adi' put within 'rum' is 'RADIUM'.
'from' acts as a link.
(Other definitions for radium that I've seen before include "Radioactive element discovered by the Curies" , "Chemical element, Ra" , "Element with symbol Ra" , "Radioactive metallic element found in pitchblende" , "Metallic element discovered by the Curies" .)