Tree much more mature than those in nursery? (5)

I believe the answer is:

elder

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

I can't explain the remainder of the clue.

(Other definitions for elder that I've seen before include "Patriarch" , "Tree - wise counsellor" , "Church official; tree" , "Shrub - church official" , "Senior tribal figure" .)

I've seen this clue in The Times.

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