Plants needing some drastic action (5)
I believe the answer is:
cacti
'plants' is the definition.
(cactus is a kind of plant)
'some drastic action' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'CACTI' is hidden in the letters of 'drastic action'.
'needing' acts as a link.
(Other definitions for cacti that I've seen before include "They're decidedly prickly" , "tuna, for example" , "Tunas" , "They store water" , "Spiny desert plants" .)