Woody tropical grass (6)
I believe the answer is:
bamboo
'woody tropical grass' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bamboo that I've seen before include "Tropical grass with strong hollow stems" , "Woody grass plant" , "Woody tropical grass with a hollow stem" , "Tropical grass/wood" , "Fast-growing woody grass" .)