The most common and most likely answer to this crossword clue is the 7 letter word UNICORN
I've seen this crossword clue in The Sunday Telegraph
U
N
I
C
O
R
N
More clues leading to the result UNICORN
- Place to learn mawkishness, a thing of legend
- At college, wow! — new fabulous creature
- It’s fabulous producing old-hat student humour?
- High-value startup company: a French one with my name
- 19 Squad not entirely associated with sentimental stuff and imaginary animal
- Horny Scottish supporter
- Vessel containing coin exchanged for fabulous creature
- College study, including reading, is a fabulous thing
- Symbol of the United Nations about right, a fabulous thing
- Sinister supporter of royal escutcheon
Buddy explains!

The straight part
We know that "Fabulous creature" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fabulous creature = unicorn.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 UNICORN mean?
UNICORN noun- A mythical beast resembling a horse or deer with a single, straight, spiraled horn projecting from its forehead.
- In various Bible translations, used to render the Latin unicornis or rhinoceros (representing Hebrew רְאֵם): a reem or wild ox.
- Any large beetle having a horn-like prominence on the head or prothorax, especially the Hercules beetle, Dynastes tityus.
- A caterpillar, Schizura unicornis, with a large thorn-like spine on the back near its head.
- The kamichi, or unicorn bird.
- A howitzer.
- Someone or something that is rare and hard to find.
- Being many (especially pastel) colours; multicoloured.
- A 15th-century Scottish gold coin worth 18 shillings, bearing the image of a unicorn.
- (sexual slang) To participate in a sexual threesome as a bisexual addition to an established heterosexual couple.
- To exceed a valuation of one billion U.S. dollars, while solely backed by venture capitalists.