Split chiefly includes this fruit (6)
I believe the answer is:
litchi
'this fruit' is the definition.
(litchi is a kind of fruit)
'split chiefly includes' is the wordplay.
'includes' indicates the answer is hidden within the clue.
'LITCHI' is hidden within 'split chiefly'.
(Other definitions for litchi that I've seen before include "Chinese tree; its fruit" , "Edible Chinese fruit" , "piece of fruit" , "Asian tree" .)