Shrew: it is cooked in casserole (5,4)
I believe the answer is:
'casserole' is the definition.
(I've seen this before)
'shrew it is cooked' is the wordplay.
'cooked' is an anagram indicator (letters cooked into a new form).
'shrewitis' with letters rearranged gives 'IRISH STEW'.
'in' acts as a link.
(Other definitions for irish stew that I've seen before include "casserole" , "National dish of potatoes, mutton and onions simmered in water" , "National dish, boiled mutton, spuds and onions" , "Traditional meat dish" , "Mutton/onion/potato dish" .)