It's found in milk container at home (6)
I believe the answer is:
casein
'it's found in milk' is the definition.
I can't tell whether this definition defines the answer.
'container at home' is the wordplay.
'container' becomes 'case' (case is a kind of container).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'case'+'in'='CASEIN'
Can you help me to learn more?
(Other definitions for casein that I've seen before include "It helps to make cheese" , "What's to be found in milk" , "Protein in milk and cheese" , "something for cheese-making" .)