Tree ring not quite in profusion (7)

I believe the answer is:

sequoia

I'm a little stuck... Click here to teach me more about this clue!

'tree' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for sequoia that I've seen before include "California redwood tree" , "Californian conifer" , "Giant conifer" , "Giant Calif. tree" , "Enormous evergreen" .)

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

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