The most common and most likely answer to this crossword clue is the 9 letter word SAILCLOTH
I've seen this crossword clue in The Guardian
S
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More clues leading to the result SAILCLOTH
Buddy explains!
The straight part
We know that "What yachtsmen hoist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what yachtsmen hoist = sailcloth.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 SAILCLOTH mean?
SAILCLOTH noun- A strong, durable fabric suitable for making sails for ships or boats.