Soft wood Ochroma Lagopus, a slab back (5)
I believe the answer is:
balsa
'soft wood' is the definition.
(I've seen this in another clue)
'a slab back' is the wordplay.
'back' shows that the letters should be reversed in order.
'a'+'slab'='aslab'
'aslab' backwards is 'BALSA'.
'ochroma lagopus' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for balsa that I've seen before include "Strong, light wood" , "Raft-making S American corkwood" , "wood for raft" , "Very light timber" , "A slab (anag.)" .)