Ultimately sage is put into bubbling stew (6)
I believe the answer is:
wisest
'ultimately sage' is the definition.
'wisest' can be an answer for 'sage' (I have seen 'Most sage' mean 'wisest' so perhaps 'sage' could also mean 'wisest'). I'm not sure about the 'ultimately' bit.
'is put into bubbling stew' is the wordplay.
I cannot quite understand how this works, but
'is' is within the answer.
an anagram of 'stew' is 'west' which is present in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for wisest that I've seen before include "Most sage and knowledgeable" , "Most judicious" , "Most astute" , "Superlatively sage" , "Most sage or experienced" .)