A shade old to enjoy existence to the full (5)

I believe the answer is:

olive

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'a shade' is the definition.
(I know that olive is a type of green)

I don't understand the remainder of the clue.

(Other definitions for olive that I've seen before include "Greyish-green; fruit" , "One [TYPE OF TREE] is from the Mediterranean" , "Cocktail fruit" , "This branch is offered to show peace" , "A Med. fruit-tree" .)

I've seen this clue in The Sunday Times and The Times.

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