The most common and most likely answer to this crossword clue is the 7 letter word CHIMNEY
I've seen this crossword clue in The Guardian
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Buddy explains!
The straight part
We know that "It’s Sooty/Sweep’s workplace" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s sooty/sweep’s workplace = chimney.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 CHIMNEY mean?
CHIMNEY noun- A vertical tube or hollow column used to emit environmentally polluting gaseous and solid matter (including but not limited to by-products of burning carbon or hydrocarbon based fuels); a flue.
- The glass flue surrounding the flame of an oil lamp.
- The smokestack of a steam locomotive.
- A narrow cleft in a rock face; a narrow vertical cave passage.
- To negotiate a chimney (narrow vertical cave passage) by pushing against the sides with back, feet, hands, etc.