Baker's proved nothing in boulangerie contains sulphur (5)
I believe the answer is:
risen
'baker's proved nothing' is the definition.
I can't judge whether this definition defines the answer.
'boulangerie contains sulphur' is the wordplay.
'boulangerie' becomes 'rien' (I can't explain this - if you can you should give a lot more credence to this answer).
'contains' is an insertion indicator.
'sulphur' becomes 'S' (synonyms).
'rien' going around 's' is 'RISEN'.
'in' is the link.
Can you help me to learn more?
(Other definitions for risen that I've seen before include "Increased" , "Suggestive of soil" , "Grown up" , "Climbed" , "(Having) come up" .)