The most common and most likely answer to this crossword clue is the 6 letter word TANKER
I've seen this crossword clue in The Daily Telegraph
T
A
N
K
E
R
More clues leading to the result TANKER
Buddy explains!
The straight part
We know that "Vessel that’s well-filled" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vessel that’s well-filled = tanker.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 TANKER mean?
TANKER noun- A tank ship, a vessel used to transport large quantities of liquid.
- A tank truck.
- A fuel tanker, petrol tanker, road tanker.
- A tank car
- Member of a tank crew, or of an armoured unit.
- A longboard.
- To transport (oil, etc.) in a tanker.