The limit starts to need adjustment in principle (4,5)
I believe the answer is:
last straw
'the limit' is the definition.
(thesaurus)
'starts to need adjustment in principle' is the wordplay.
'to need adjustment' is an anagram indicator.
'in' means one lot of letters goes inside another.
'principle' becomes 'law' (I've seen this in another clue).
'starts' anagrammed gives 'ststra'.
'ststra' going within 'law' is 'LAST STRAW'.
(Other definitions for last straw that I've seen before include "Downfall of the laden camel" , "Small event finally causing a problem" , "The one that breaks the camel's back" , "Start laws (anag) ? breaking point?" , "proved back-breaking" .)