Thrash from French heavy metal artist's empty (6)
I believe the answer is:
defeat
'thrash' is the definition.
(thesaurus)
'from french heavy metal artist's empty' is the wordplay.
'from french' becomes 'de' (French for 'from').
'heavy metal' becomes 'fe' (chemical symbol for iron).
'empty' means to remove the middle letters.
'artist' with its middle taken out is 'at'.
'de'+'fe'+'at'='DEFEAT'
(Other definitions for defeat that I've seen before include "Loss" , "Gain victory over" , "Win over, frustrate" , "failure" , "Conquest" .)