Generally then I cooked with Mum at home (2,3,4)
I believe the answer is:
in the main
'generally' is the definition.
(I've seen this before)
'then i cooked with mum at home' is the wordplay.
'cooked' indicates an anagram (letters cooked into a new form).
'with' says to put letters next to each other.
'mum' becomes 'ma' (both can mean mother).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'then'+'i'='theni'
'theni' anagrammed gives 'inthe'.
'inthe'+'ma'+'in'='IN THE MAIN'
(Other definitions for in the main that I've seen before include "Where cod and haddock may be found" , "usually" , "seaborne?" , "Swimming" , "Where piped water collects" .)