The most common and most likely answer to this crossword clue is the 8 letter word SHADDOCK
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Buddy explains!

The straight part
We know that "Pomelo" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pomelo = shaddock.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SHADDOCK mean?
SHADDOCK noun- The large fruit of the Citrus maxima (syn. C. grandis), native to South Asia and Southeast Asia, with a thick green or yellow rind, a thick white pith, and semi-sweet translucent pale flesh.
- The tree which produces this fruit.
- The grapefruit.