Breaking law, go on conceding this is a mistake (3,4)
I believe the answer is:
own goal
'a mistake' is the definition.
(I've seen this before)
'breaking law go on' is the wordplay.
'breaking' indicates an anagram.
'law'+'go'+'on'='lawgoon'
'lawgoon' with letters rearranged gives 'OWN GOAL'.
'conceding this is' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for own goal that I've seen before include "embarrassing error" , "(Soccer) score which helps opposing team" , "Self-inflicted loss" , "move that backfired?" , "unintentional problem for herself, say" .)