The most common and most likely answer to this crossword clue is the 8 letter word COXSWAIN
I've seen this crossword clue in The Guardian
C
O
X
S
W
A
I
N
More clues leading to the result COXSWAIN
- One steering apple cart around heading for street
- Helmsman to steer south-west, carried by third person
- With craft I can steer 225º through opening
- Ten was poorly invested in money for boater
- Vote was rigged, splitting hard cash for director on board
- Firm kiss by lover for keeper of course
- Steer away from NE, in the clutches of first son as helmsman
- One over the eight?
- Helmsman’s male lover follows commanding officer at ten
- Company crosses finish first, embracing a crew member
Buddy explains!

The straight part
We know that "boater" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case boater = coxswain.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 COXSWAIN mean?
COXSWAIN noun- In a ship's boat, the helmsman given charge of the boat's crew.
- The member of a crew who steers the shell and coordinates the power and rhythm of the rowers.
- The second or third mate of a vessel, in charge of the master's barge.
- A rank or position.
- (intransative) To act as coxswain for.