Spiny succulent plant (6)
I believe the answer is:
cactus
'spiny succulent plant' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cactus that I've seen before include "Thorny desert plant" , "Succulent desert plant" , "Spiney plant of dry areas" , "Often prickly succulent plant native to arid regions" , "Prickly sort" .)