Woody tropical grass (6)
I believe the answer is:
bamboo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">woody tropical grass</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)