Fruit garden oddly busy (9)
I believe the answer is:
greengage
'fruit' is the definition.
(type of plum)
'garden oddly busy' is the wordplay.
'oddly' indicates alternate letters (letters in odd-numbered positions).
'busy' becomes 'engage' (I am not sure about this - if you are sure you should believe this answer much more).
The alternating letters of 'garden' are 'gre'.
'gre'+'engage'='GREENGAGE'
Can you help me to learn more?
(Other definitions for greengage that I've seen before include "Greenish-yellow type of plum" , "Fruit akin to plum" , "Such a summer novel" , "Plum-like fruit" , "Variety of plum" .)