The most common and most likely answer to this crossword clue is the 9 letter word TARANTULA
I've seen this crossword clue in The Guardian
T
A
R
A
N
T
U
L
A
More clues leading to the result TARANTULA
- Scary spinner's natural bent among reserves
- Sailor left aunt, worried inside by a spider
- Being hairy thanks to a natural mutation
- Sailor and soldier regularly unload arthropod
- Angry words with Greek character about the French being … hairy
- Former quiz show host losing heart with stripped Disney heroine revealing something hairy
- Thanks to natural evolution, it has a serious bite
- Jack upsets aunt with the French spider
- Spider coming from altar – aunt going berserk
- Not entirely brown design natural for large arachnid
Buddy explains!

The straight part
We know that "spider" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case spider = tarantula.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 TARANTULA mean?
TARANTULA noun- Any of the large, hairy New World spiders comprising the family Theraphosidae.
- (by extension) A member of certain other groups of spiders, generally characterized by large size, hairiness, or membership of infraorder Mygalomorphae to which Theraphosidae family also belongs.
- A species of wolf spider, Lycosa tarantula, native to southern Europe, the mildly poisonous bite of which was once thought to cause an extreme urge to dance (tarantism).