As extracted from yeast, nevertheless (3)
I believe the answer is:
yet
'nevertheless' is the definition.
(I know that nevertheless can be written as yet)
'as extracted from yeast' is the wordplay.
'extracted from' is a deletion indicator.
'yeast' with 'as' taken away is 'YET'.
(Other definitions for yet that I've seen before include "Still, even" , "Still, so far" , "in spite of that" , "Though; still" , "Still; nevertheless" .)