Game over with error and legal oversight (8)
I believe the answer is:
loophole
'game' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for loophole that I've seen before include "Escape clause" , "Mistake in legislation" , "Exploited legal ambiguity" , "way to escape penalty" , "Means of evasion" .)