The most common and most likely answer to this crossword clue is the 10 letter word SUPERCARGO
I've seen this crossword clue in The Times
S
U
P
E
R
C
A
R
G
O
More clues leading to the result SUPERCARGO
- GCSE uproar -- distraught organiser at sea
- Ship’s officer therefore rings RAC up, following matter arising
- Procure gas at sea for crew member
- Crew member has to leave after drink with queen and Charles
- Excellent vehicle for good old ship employee-trader
- Wild cougars circling the westbound salesman and the ship's officer
- Sailor selling freight caught on board A1 Greek ship
- Ship’s goods overseer is to set off chasing a Lamborghini?
- Drink ruined a grocer at sea — he does have loads on his mind
Buddy explains!

The straight part
We know that "organiser at sea" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case organiser at sea = supercargo.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 SUPERCARGO mean?
SUPERCARGO noun- An officer on board a merchant ship who has charge of the cargo and its turnover (or the senior of two if one has two, the other being the subcargo; usually historical, since nowadays a person with such a job would remain on shore).