Each cat essentially spies a tree (6)

I believe the answer is:

acacia

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

'each cat essentially spies' is the wordplay.
'each' becomes 'ac' (I can't explain this - if you can you should believe this answer much more).
'essentially' indicates the central letters.
'spies' becomes 'CIA' (Central Intelligence Agency).
The middle letter of 'cat' is 'a'.
'ac'+'a'+'cia'='ACACIA'

Can you help me to learn more?

(Other definitions for acacia that I've seen before include "Plant of the mimosa family" , "ornamental tree" , "Spiny tree of warm climates" , "Garden shrub, also known as wattle" , "Spiny tree or shrub" .)

I've seen this clue in The Guardian.

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