Cheery pat incensed oldest model (9)

I believe the answer is:

archetype

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

'model' is the definition.
(I know that archetype is a type of archetype)

'cheery pat incensed oldest' is the wordplay.
'cheery pat' can be anagrammed to 'ARCHETYPE'.
However, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for archetype that I've seen before include "Original pattern or model" , "Model - perfect specimen" , "Perfect example" , "Very typical example" , "Original mode" .)

I've seen this clue in the Sydney Morning Herald.

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