Tree of painful memories? (5)

I believe the answer is:

birch

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'tree' is the definition.
(I've seen this before)

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

(Other definitions for birch that I've seen before include "Wood" , "Silver-white barked tree" , "Tree with silvery bark" , "See 1" , "Hardy tree" .)

I've seen this clue in the Evening Standard.

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