Pudding dish for seconds, more or less after milk (7)
I believe the answer is:
tapioca
'pudding' is the definition.
(tapioca pudding is a kind of pudding)
'dish for seconds more or less after milk' is the wordplay.
I cannot really see how this works, but
'milk' could be 'tap' (both can mean to exploit or use) and 'tap' is found in the answer.
'more or less' could be 'c' (abbreviation for 'circa', meaning approximately) and 'c' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tapioca that I've seen before include "Starch from cassava used in making puddings" , "I act OAP (anag) - edible substance made from cassava" , "dessert" , "Pudding made from an extract of cassava" , "Pudding maker" .)