The most common and most likely answer to this crossword clue is the 8 letter word JOINTERS
J
O
I
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S
Buddy explains!
The straight part
We know that "planes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case planes = jointers.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 JOINTERS mean?
JOINTERS noun- One that joints.
- Any of various tools used to construct or finish joints, especially:
- An equivalent machine, notably used to produce a flat surface on boards.