Drink may seem large but is actually quite small (8)

I believe the answer is:

pintsize

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'seem large but is actually quite small' is the definition.
I can't judge whether this defines the answer.

'drink may' is the wordplay.
'drink' becomes 'pint' (pint is a unit of liquid volume).
'may' becomes 'size' (I can't justify this - if you can you should believe this answer much more).
'pint'+'size'='PINTSIZE'

Can you help me to learn more?

I've seen this clue in The Irish Times.

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