The most common and most likely answer to this crossword clue is the 8 letter word MANURING
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The straight part
We know that "Dressing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dressing = manuring.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 MANURING mean?
MANURING verb- To cultivate by manual labor; to till; hence, to develop by culture.
- To apply manure (as fertilizer or soil improver).
- An application of manure.