As yet developing growth on grape vine (5)
I believe the answer is:
yeast
'growth on grape vine' is the definition.
The answer and definition can be both plants as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'as yet developing' is the wordplay.
'developing' indicates an anagram (letters developed into a new form).
'as'+'yet'='asyet'
'asyet' anagrammed gives 'YEAST'.
Can you help me to learn more?
(Other definitions for yeast that I've seen before include "It makes dough rise" , "Androgynous" , "Bread-making component" , "Brewer" , "Organism causing fermentation" .)