The most common and most likely answer to this crossword clue is the 8 letter word LANDSMEN
I've seen this crossword clue in The Guardian
L
A
N
D
S
M
E
N
Buddy explains!
The straight part
We know that "they’re no sailors" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they’re no sailors = landsmen.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 LANDSMEN mean?
LANDSMEN noun- The opposite of a seaman. A person who does not go to sea, who lacks the skills of a sailor or who is uncomfortable on ships or boats.
- (oil and gas industry) A person who negotiates leases, contracts and other business deals between producers and landowners.
- A fellow Jew who comes from the same district or town, especially in Eastern Europe
- Someone of a similar heritage or belief system
- A military rank given to naval recruits