Dish served thus every Wednesday, initially (4)
I believe the answer is:
stew
'dish' is the definition.
(type of dish)
'served thus every wednesday initially' is the wordplay.
'initially' indicates taking the first letters.
The first letters of 'served thus every wednesday' is 'STEW'.
(Other definitions for stew that I've seen before include "Dish of meat and vegetables cooked slowly in liquid" , "Get anxious" , "anxious state" , "Casserole" , "Meat and veg dish" .)