Do finish off (7)
I believe the answer is:
execute
This clue is a double definition.
'do' is the first definition.
(executing is a kind of doing)
'finish off' is the second definition.
(thesaurus)
(Other definitions for execute that I've seen before include "Kill someone" , "Put to death or carry out, say plan" , "Guillotine" , "Carry into effect" , "Perform or kill legally" .)