Light timber a hunk hauled back (5)

I believe the answer is:

balsa

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'light timber' is the definition.
'balsa' can be an answer for 'timber' (I've seen this before). I am unsure of the 'light' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for balsa that I've seen before include "Tree with light soft wood" , "Very lightweight wood from tropical tree" , "Tree yielding light wood" , "Very light wood in a slab" , "Raft-making S American corkwood" .)

I've seen this clue in The Sun.

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