The most common and most likely answer to this crossword clue is the 8 letter word CANOEIST
I've seen this crossword clue in The Daily Telegraph
C
A
N
O
E
I
S
T
More clues leading to the result CANOEIST
- Expert in water, ocean, flexible at first
- Boatman is at once overturned
- Someone on the water at once is at sea
- He’ll sit uncomfortably on rough ocean
- Boater at once is fashionable
- Turbulent ocean — it’s damaged small boat’s propeller
- Person in boat in ocean — it’s turbulent
- One floats along ocean, capsizing first?
- Boater is at once showing wear and tear
- Stormy section engulfs a water sportsperson
Buddy explains!
The straight part
We know that "one in kayak" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one in kayak = canoeist.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.