Clinging vine (3)
I believe the answer is:
ivy
'clinging vine' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ivy that I've seen before include "Parasitical plant, companion to holly" , "Poisonous plant" , "The Hedera genus of evergreen climbers" , "Old World vine" , "Climbing plant, associated with holly" .)