Call for building material (6)

I believe the answer is:

timber

I'm a little stuck... Click here to teach me more about this clue!

'building material' is the definition.
(I know this)

I don't understand how the remainder of the clue works.

(Other definitions for timber that I've seen before include "wooden" , "Deal possibly" , "board" , "Wood for building, etc" , "Ash perhaps" .)

I've seen this clue in The Mirror.

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