Water-resistant wood (4)
I believe the answer is:
teak
'water-resistant wood' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for teak that I've seen before include "Hardwood found naturally in the Far East" , "A SE Asian hardwood" , "Heavy wood of a tall evergreen Asian tree" , "Strong heavy wood of an Asian tree" , "Type of wood" .)