The most common and most likely answer to this crossword clue is the 7 letter word ROOFING
I've seen this crossword clue in Financial Times
R
O
O
F
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More clues leading to the result ROOFING
Buddy explains!

The straight part
We know that "building work" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case building work = roofing.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 ROOFING mean?
ROOFING noun- Material used on the outside of a roof, such as shingles.
- A way of travel which consists in clambering over the roofs of skyscrapers.
- To cover or furnish with a roof.
- To traverse buildings by walking or climbing across their roofs.
- To put into prison, to bird.
- To shelter as if under a roof.