Key (B not A, then E) going to pot (8)
I believe the answer is:
crucible
'to pot' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for crucible that I've seen before include "smelting vessel" , "Metal-melting container" , "Vessel for melting metals" , "Melting pot" , "severe test" .)