One middle-sized character's after leads in 'Pickwick' and 'Hamilton' -- mug! (4)

I believe the answer is:

phiz

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'hamilton mug' is the definition.
'phiz' can be an answer for 'mug' (thesaurus). I'm unsure of the 'hamilton' bit.

'one middle-sized character's after leads in pickwick' is the wordplay.
'one middle-sized' becomes 'hi' (I can't explain this - if you can you should believe this answer much more).
'character' becomes 'z'.
'after' is a charade indicator (letters next to each other).
'leads in' says to take the initial letters (I've seen 'lead in' mean this).
The initial letter of 'pickwick' is 'p'.
'hi'+'z'='hiz'
'hiz' after 'p' is 'PHIZ'.

'and' acts as a link.

Can you help me to learn more?

(Other definitions for phiz that I've seen before include "Facial expression" , "Dickens's illustrator" , "mug" , "Dial" , "Face" .)

I've seen this clue in The Telegraph.

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