The most common and most likely answer to this crossword clue is the 7 letter word NAVVIES
I've seen this crossword clue in The Daily Telegraph
N
A
V
V
I
E
S
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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 NAVVIES mean?
NAVVIES noun- A laborer on a civil engineering project such as a canal or railroad.
- To carry out physical labor on a civil engineering project.