Plant runner (7)
I believe the answer is:
tendril
'plant runner' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tendril that I've seen before include "Clinging part of a plant" , "Slender curl or plant climber" , "Climbing plant's grasper" , "A creeper, or a curl of hair" , "Twining shoot" .)