The most common and most likely answer to this crossword clue is the 4 letter word NIPA
N
I
P
A
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The straight part
We know that "Palm tree" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case palm tree = nipa.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 NIPA mean?
NIPA noun- A palm tree of the species Nypa fruticans.
- A liquor made from the sap of nipa palm.
- The leaves of the nipa palm, when used as a material for thatching, basketry or other uses.
- Distichlis palmeri, a saltgrass native to the Sonoran Desert of Mexico and the United States, Palmer's grass.