Unknown bearing ingredient for bread? (5)
I believe the answer is:
yeast
'ingredient for bread?' is the definition.
I can't judge whether this definition defines the answer.
'unknown bearing' is the wordplay.
'unknown' becomes 'y' (algebra).
'bearing' becomes 'east' (a compass bearing).
'y'+'east'='YEAST'
Can you help me to learn more?
(Other definitions for yeast that I've seen before include "Alcohol-producing fungus" , "Brewer" , "Dough raising agent" , "Baker's raising agent" , "Fungus used to ferment sugar" .)