Easy? Not terribly, for the dimwitted (9)

I believe the answer is:

simpleton

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'the dimwitted' is the definition.
I can't judge whether this definition defines the answer.

'easy? not terribly' is the wordplay.
'easy?' becomes 'simple' ('simple' is associated in meaning with 'easy').
'terribly' is an anagram indicator.
'not' anagrammed gives 'ton'.
'simple'+'ton'='SIMPLETON'

'for' acts as a link.

Can you help me to learn more?

(Other definitions for simpleton that I've seen before include "Idiot" , "Dope" , "Unintelligent person" , "Blockhead" , "Fool" .)

I've seen this clue in the Evening Standard.

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