The most common and most likely answer to this crossword clue is the 3 plus 5 letter word SEA CHEST
I've seen this crossword clue in The Times
S
E
A
C
H
E
S
T
Buddy explains!
The straight part
We know that "The case sailor originally transported?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the case sailor originally transported? = sea chest.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.