Cadet wanting adult in plane? (4)

I believe the answer is:

tree

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'plane?' is the definition.
(plane tree is a type of tree)

I don't understand the remainder of the clue.

(Other definitions for tree that I've seen before include "Tall, woody plant" , "Eg, elm or oak" , "Diagram representing different relationships" , "Large plant with trunk" , "Eg, laburnum" .)

I've seen this clue in The Independent.

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