Refined sources of metal extremely well! (8,2)
I believe the answer is:
gracious me
'well' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'refined sources of metal extremely' is the wordplay.
'refined' becomes 'gracious' (similar in meaning).
'sources of' suggests taking the first letters (the beginning of a word is its sauce).
The first letters of 'metal extremely' is 'me'.
'gracious'+'me'='GRACIOUS ME'
Can you help me to learn more?
(Other definitions for gracious me that I've seen before include "Mamma Mia!" , "Gordon Bennett" .)