The most common and most likely answer to this crossword clue is the 9 letter word MAYFLOWER
I've seen this crossword clue in Independent
M
A
Y
F
L
O
W
E
R
More clues leading to the result MAYFLOWER
- Is not certain to pick vessel for transatlantic voyage
- Arbutus is not certain to blossom
- Incredibly low fare with my old transport
- Historic ship has the potential to succeed?
- Can fellow reduce the price of spring plant?
- Shrub won’t necessarily 7
- Hawthorn may blossom on transatlantic ship
- Ship could move like water? I’m not sure
- Garden equipment trapping poor fly on a plant
- PM fine with second-class transportation to America once
Buddy explains!

The straight part
We know that "Historic ship" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case historic ship = mayflower.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 MAYFLOWER mean?
MAYFLOWER noun- Any of several plants that flower in May - especially the hawthorn (in Britain) and the trailing arbutus (in the US).