In central Java, Jock saw odd box tree (7)

I believe the answer is:

avocado

'tree' is the definition.
(avocado tree is a kind of tree)

I can't explain the rest of the clue.

(Other definitions for avocado that I've seen before include "Pear-shaped tropical fruit" , "Dull greenish colour" , "Green - fruit eaten as a vegetable" , "Light green; fruit" , "A posh tropical pear" .)

I've seen this clue in The Times.

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