She initially goes into action, having responsibility for food (9)
I believe the answer is:
'food' is the definition.
(casserole is a kind of food)
'she initially goes into action having responsibility' is the wordplay.
'initially' says to take the initial letters.
'goes into' means one lot of letters goes inside another.
'action' becomes 'case' (synonyms).
'having responsibility' becomes 'role' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'she' is 's'.
's' inserted into 'case' is 'casse'.
'for' is the link.
Can you help me to learn more?
(Other definitions for casserole that I've seen before include "Stew; dish" , "meal" , "Slow-cooked dish" , "Kind of stew" , "Meat dish" .)