The most common and most likely answer to this crossword clue is the 6 letter word CACTUS
C
A
C
T
U
S
More clues leading to the result CACTUS
- Clubs do something with American plant
- Congress initially take steps to get American plant
- Part of magic act uses plant
- Caught you and me in the act? No!
- Desert plant around Connecticut
- ‘Living rock’, say, from Coldplay? Not them
- Plant copper on front of street outside a court
- Prickly sort in court engaged in endless legal action
- Conservative legislation covering leader of union in plant
- Copper, special originally, eating something done that’s succulent
Buddy explains!

The straight part
We know that "spiny plant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case spiny plant = cactus.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 CACTUS mean?
CACTUS noun- Any member of the family Cactaceae, a family of flowering New World succulent plants suited to a hot, semi-desert climate.
- Any succulent plant with a thick fleshy stem bearing spines but no leaves, such as euphorbs.
- Non-functional, broken, exhausted, dead.