Baker's proved nothing in boulangerie contains sulphur (5)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

RIEN (“nothing” in French, so as it would be spoken in a boulangerie = French baker’s shop) containing S (chemical symbol for sulphur). In baking, dough is left to “prove” = rise = expand as the yeast produces carbon dioxide.