The most common and most likely answer to this crossword clue is the 3 plus 5 letter word ARK ROYAL
I've seen this crossword clue in The Guardian
A
R
K
R
O
Y
A
L
More clues leading to the result ARK ROYAL
Buddy explains!

The straight part
We know that "Old craft" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old craft = ark royal.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.