Plant's climbing organ (7)
I believe the answer is:
tendril
'plant's climbing organ' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tendril that I've seen before include "Clinging part of a plant" , "Coiling shoot of climbing plant" , "Natural thread climbing plants produce to attach to a support" , "Climbing plant's supporter" , "Twisted lock of hair" .)