Some act with dunderhead (4)

I believe the answer is:

twit

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'dunderhead' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?

'some act with' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'TWIT' is hidden within 'act with'.

Can you help me to learn more?

(Other definitions for twit that I've seen before include "Blockhead" , "Taunt; fool" , "Nincompoop" , "Bait - fool" , "Twerp" .)

I've seen this clue in The Sun.

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