The most common and most likely answer to this crossword clue is the 6 letter word SALADE
S
A
L
A
D
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Buddy explains!
The straight part
We know that "Medieval helmet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case medieval helmet = salade.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 SALADE mean?
SALADE noun- A kind of helmet; a sallet.
- A food made primarily of a mixture of raw or cold ingredients, typically vegetables, usually served with a dressing such as vinegar or mayonnaise.
- A raw vegetable of the kind used in salads.