The most common and most likely answer to this crossword clue is the 5 letter word MANTA
I've seen this crossword clue in Financial Times
M
A
N
T
A
More clues leading to the result MANTA
Buddy explains!

The straight part
We know that "Ray" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ray = manta.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 MANTA mean?
MANTA noun- A kind of fabric or blanket used in Latin America and southwestern United States.
- Any of several very large pelagic rays of the genus Manta, with winglike pectoral fins, a long tail, and two fins resembling horns that project from the head.