The most common and most likely answer to this crossword clue is the 7 letter word TRIREME
T
R
I
R
E
M
E
More clues leading to the result TRIREME
- Reported experiment with paper boat long ago
- Galley test sheets discussed
- Once docked, tried to get some sleep aboard ancient vessel
- Three banks pulling together kept it afloat
- Flag setter placed around Republican ship
- Initially tactless French laugh at yours truly’s craft
- Reportedly go with engineers in ancient boat
- First to row in weary setter’s boat
- Engineers coming in to decorate English ship
- Empty tanker takes on one army corps for Greek warship
Buddy explains!

The straight part
We know that "a boat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a boat = trireme.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 TRIREME mean?
TRIREME noun- (history) A galley with three banks of oars, one above the other, used mainly as a warship.