Scottish dish made from sheep's or calf's offal, oatmeal, suet and seasonings boiled in a skin made from the animal's stomach (6)
I believe the answer is:
haggis
(Other definitions for haggis that I've seen before include "Scottish offal dish" , "Scottish savoury combining lamb offal and oatmeal" , "Hi gags about traditional Scottish dish" , "Burns' night dish" , "Dish boiled in a skin made from an animal's stomach" .)