Usage follows one State for a recipe in a casing (7)
I believe the answer is:
sausage
'recipe in a casing' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'usage follows one state' is the wordplay.
'follows' means one lot of letters go next to another.
'one state' becomes 'SA' (South Australia).
'usage' after 'sa' is 'SAUSAGE'.
'for a' is the link.
Can you help me to learn more?
(Other definitions for sausage that I've seen before include "Part of a hot dog" , "Chipolata, for example" , "Not a - means nothing" , "Assuage with tasty meat roll" , "Eg, salami or cervelat" .)