The most common and most likely answer to this crossword clue is the 6 plus 7 letter word PADDLE STEAMER
I've seen this crossword clue in The Daily Telegraph
P
A
D
D
L
E
S
T
E
A
M
E
R
More clues leading to the result PADDLE STEAMER
- Confuses players coming in by boat
- Hesitation under pressure confuses crew in boat
- Prince mixes up crew on main royal vessel
- Somehow mastered deal on pressure vessel
- Pressure confuses crew on Queen Elizabeth and another vessel
- Master pleaded for change of ship
- Males departed, travelling by boat
- Plastered dame at sea in boat
- Confuses group stopping for each riverboat
- A stepladder designed to get me on board boat
Buddy explains!
The straight part
We know that "riverboat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case riverboat = paddle steamer.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.