Raft wood (5)
I believe the answer is:
balsa
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">raft wood</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for balsa that I've seen before include "Tree yielding light wood" , "lightweight boat-builder" , "Very light wood in a slab" , "Raft-making S American corkwood" , "Tropical American tree" .)