Insect in tree it damaged, feeding on elm, ultimately (7)

I believe the answer is:

termite

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'insect' is the definition.
(I know that termite is a type of insect)

I can't explain the rest of the clue.

(Other definitions for termite that I've seen before include "Six-footer" , "It lives on wood" , "Mound-building insect" , "Ant-like insect which destroys timber" , "Mound-dweller" .)

I've seen this clue in The Guardian.

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