The most common and most likely answer to this crossword clue is the 11 letter word DILAPIDATED
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The straight part
We know that "in rotten condition" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in rotten condition = dilapidated.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 DILAPIDATED mean?
DILAPIDATED verb- To fall into ruin or disuse.
- To cause to become ruined or put into disrepair.
- To squander or waste.
- Having fallen into a state of disrepair or deterioration, especially through neglect.