Upset the applecart - darn, it's all in (4,3,6)
I believe the answer is:
part and parcel
'all in' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'upset the applecart darn' is the wordplay.
'upset' is an anagram indicator.
'applecart'+'darn'='applecartdarn'
'applecartdarn' is an anagram of 'PART AND PARCEL'.
'it's' is the link.
Can you help me to learn more?
(Other definitions for part and parcel that I've seen before include "Essential component (of something)" , "Essential element of something" , "Essentially a component (of)" , "that's an essential item" , "Essential ingredient" .)