Attack puts one out (3,4)
I believe the answer is:
set upon
'attack' is the definition.
(setting upon is a kind of attacking)
'puts one out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'puts'+'one'='putsone'
'putsone' is an anagram of 'SET UPON'.
(Other definitions for set upon that I've seen before include "Determined to do (something)" , "Attack" , "Attacked" , "Mug" .)