The tall grass (6)
I believe the answer is:
bamboo
'the tall grass' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bamboo that I've seen before include "Thick tropical cane" , "Woody tropical grass with a hollow stem" , "Panda's dinner?" , "Mature canes used making furniture" , "Fast-growing woody grass" .)