In dramatic act used spiny plant (6)
I believe the answer is:
cactus
'spiny plant' is the definition.
(I've seen this before)
'in dramatic act used' is the wordplay.
'in' says the answer is hidden in the clue.
'CACTUS' can be found hidden inside 'dramatic act used'.
(Other definitions for cactus that I've seen before include "Spiky desert plant" , "Prickly sort" , "Eg, prickly pear" , "Often prickly succulent plant native to arid regions" , "Thorny desert plant" .)