Child's pet name for the chips - of course, it's essential for any takeaway
I believe the answer is:
doggy bag
'any takeaway' is the definition.
The definition suggests a singular noun which matches the answer.
'child's pet name for the chips of course it's essential' is the wordplay.
I cannot quite see how this works, but
'pet' could be 'dog' and 'dog' is present in the answer.
'name' could be 'ag' and 'ag' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'for' is the link.
Can you help me to learn more?
(Other definitions for doggy bag that I've seen before include "For restaurant food that a customer didn't eat" , "Party leftover container" , "Leftovers receptacle" , "It's for when one orders too much when eating out" , "Container for what you can't eat when dining out" .)