Call in state sauce (4)
I believe the answer is:
soya
'sauce' is the definition.
(I have seen 'Dark sauce ' mean 'soya' so perhaps 'sauce' could also mean 'soya')
'call in state' is the wordplay.
'call' becomes 'oy' (I can't justify this - if you can you should believe this answer much more).
'in' indicates putting letters inside.
'state' becomes 'SA' (South Australia).
'oy' going inside 'sa' is 'SOYA'.
Can you help me to learn more?
(Other definitions for soya that I've seen before include "Asian bean yielding edible oil and flour" , "Bean used in dark sauce" , "Plant producing beans" , "Protein-rich bean" , "Vegetable with very high protein" .)