Twain’s Tom’s outspoken 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')
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for soya that I've seen before include "Kind of bean" , "Dark salty sauce" , "Asian bean yielding edible oil and flour" , "Plant grown for its beans" , "Protein-rich vegetable" .)