Action that backfired? Individual shot a line (3,4)
I believe the answer is:
own goal
'action that backfired?' is the definition.
(I've seen this before)
'individual shot a line' is the wordplay.
'individual' becomes 'own'.
'shot' becomes 'go' (I've seen this in other clues**).
'line' becomes 'l'.
'own'+'go'+'a'+'l'='OWN GOAL'
(Other definitions for own goal that I've seen before include "Shooting oneself in the foot" , "Self-inflicted loss" , "Act harming the perpetrator's interests" , "Disadvantageous move for the party making it" , "Self-inflicted disadvantage, from soccer" .)