Wood: a chunk hauled up (5)
I believe the answer is:
balsa
'wood' is the definition.
(balsa is a kind of wood)
'a chunk hauled up' is the wordplay.
'chunk' becomes 'slab' (I've seen this in another clue).
'hauled up' says the letters should be written in reverse.
'a'+'slab'='aslab'
'aslab' backwards is 'BALSA'.
(Other definitions for balsa that I've seen before include "Tropical American tree" , "A slab (anag.)" , "lightweight boat-builder" , "Wood used by model makers" , "Very lightweight wood from tropical tree" .)