The most common and most likely answer to this crossword clue is the 7 letter word CARAVEL
I've seen this crossword clue in The Sunday Telegraph
C
A
R
A
V
E
L
Buddy explains!

The straight part
We know that "Spanish ship" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case spanish ship = caravel.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 CARAVEL mean?
CARAVEL noun- A light, usually lateen-rigged sailing ship used by the Portuguese and Spanish for about 300 years from the 15th century, first for trade and later for voyages of exploration.