Bring back a slab of light wood (5)
I believe the answer is:
balsa
'light wood' is the definition.
(I've seen this before)
'bring back a slab' is the wordplay.
'bring back' shows that the letters should be reversed in order.
'a'+'slab'='aslab'
'aslab' in reverse letter order is 'BALSA'.
'of' acts as a link.
(Other definitions for balsa that I've seen before include "Very light timber" , "wood for raft" , "Tree with light soft wood" , "light raft" , "A slab (anag.)" .)