The most common and most likely answer to this crossword clue is the 11 letter word GROUNDSHEET
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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 GROUNDSHEET mean?
GROUNDSHEET noun- A sheet of waterproof material that is spread on the ground, often beneath a tent, and upon which a person may sit or sleep.