Executed many a person (4)
I believe the answer is:
done
'executed' is the definition.
(execute can mean to do or accomplish)
'many a person' is the wordplay.
'many' becomes 'D' (Roman numeral for 500).
'a person' becomes 'one' (an individual).
'd'+'one'='DONE'
(Other definitions for done that I've seen before include "This sort of thing is socially acceptable" , "Swindled" , "Tricked" , "Performed" , "Finished like node" .)