More mature fruit used to make wine (10)
I believe the answer is:
elderberry
'fruit used to make wine' is the definition.
(I've seen this before)
'more mature' is the wordplay.
I cannot quite see how this works, but
'more mature' could be 'elder' (I've seen this before) and 'elder' is found in the answer.
The remaining letters 'berry' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for elderberry that I've seen before include "Fruit used to make wine" , "Wine or jelly can be made from this" , "Fruit used for home-made wine" , "Fruit used for cordial" , "Tree fruit used for wine" .)