White part of an orange (4)
I believe the answer is:
pith
'white part of an orange' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pith that I've seen before include "Tissue beneath citrus fruit rind" , "Inside skin of, say, orange" , "Spongy tissue like that lining an orange skin" , "nub of matter" , "Fibrous part of fruit - essence" .)