Possible Clues:

• Dough-raising need
• Naturally powered elevator?
• Fermentation ingredient
• Bakery leavener
• Gets a rise from positive response on street
• It can raise dough
• It's used to raise dough
• Does fellow making a casual few quid get a rise out of this? Only if he gives it to Nan
• It can raise some dough
• You put on a stone — that'll create ferment