'Pint?' 'Very much so!' (3,4)

I believe the answer is:

not half

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'very much so' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for not half that I've seen before include "I agree 100%" , "Very much, greatly" , "unequal share for you or me" , "One hundred per cent!" , "I couldn't agree more!" .)

I've seen this clue in The Telegraph.

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