The most common and most likely answer to this crossword clue is the 9 letter word STEAMBOAT
I've seen this crossword clue in The Guardian
S
T
E
A
M
B
O
A
T
More clues leading to the result STEAMBOAT
- Sailing vessel's crew stole through empty street
- Vessel settled — on board, crew starts to bail out
- … male snake pursuing meal in street – it puffs out when moving
- Boast outrageously about crew in 2
- Carnivore eats English lamb leaving the head in a vessel
- Second eleven cricketer bagging duck — an old 20, perhaps
- Ship‘s second crew facing stick hiding nothing
- Tom Bates messed about, holding a vessel
- Vessel requiring a mast to be re-rigged
- Ship’s mate’s abnormal love in club
Buddy explains!

The straight part
We know that "an old 20, perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an old 20, perhaps = steamboat.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 STEAMBOAT mean?
STEAMBOAT noun- A boat or vessel propelled by steam power.
- Hot pot (Chinese dish).
- To travel by steamboat.