Starts off breaking regulation -- that's the limit! (4,5)
I believe the answer is:
last straw
'the limit' is the definition.
(thesaurus)
'starts off breaking regulation' is the wordplay.
'off' indicates an anagram.
'breaking' is an insertion indicator.
'regulation' becomes 'law' (I've seen this before).
'starts' anagrammed gives 'ststra'.
'ststra' inserted into 'law' is 'LAST STRAW'.
'that's' is the link.
(Other definitions for last straw that I've seen before include "Something tipping the balance" , "The final irritation that stretches your patience beyond the limit" , "The end of the harvest" , "That which broke the camel's back?" , "drinker was lucky to get?" .)