Self-inflicted loss (3,4)
I believe the answer is:
own goal
'self-inflicted loss' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for own goal that I've seen before include "Football score at the wrong end" , "Football mishap" , "Act harming one's personal interests" , "Costly footballing error" , "Act harming the perpetrator's interests" .)