The most common and most likely answer to this crossword clue is the 4 letter word YUZU
Y
U
Z
U
Buddy explains!
The straight part
We know that "plant product" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plant product = yuzu.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 YUZU mean?
YUZU noun- A citrus fruit originating in East Asia, Citrus ichangensis x Citrus reticulata var. austera.