Fresh, good and mature fruit (9)
I believe the answer is:
greengage
'fruit' is the definition.
(type of plum)
'fresh good and mature' is the wordplay.
'fresh' becomes 'green' (I've seen this before).
'good' becomes 'g' (abbreviation).
'and' means one lot of letters go next to another.
'mature' becomes 'age' (synonyms).
'green'+'g'+'age'='GREENGAGE'
(Other definitions for greengage that I've seen before include "Such a summer novel" , "Fruit tree" , "Greenish-yellow type of plum" , "Plum-like fruit" , "Variety of plum" .)