Tree is more bare, having top removed (5)

I believe the answer is:

alder

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'tree' is the definition.
(alder tree is a kind of tree)

I don't understand the rest of the clue.

(Other definitions for alder that I've seen before include "Tree or shrub whose wood is resistant to underwater rot" , "Tree whose bark is used in tanning" , "Catkin-bearing tree" , "Tree with toothed leaves and cone-like fruits" , "A tree for Adler" .)

I've seen this clue in The Times.

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