With one cold, each barrel holds summer treats (3-6)

I believe the answer is:

ice-blocks

I'm a little stuck... Click here to teach me more about this clue!

'with one cold each' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'barrel holds summer treats' is the wordplay.
'barrel' becomes 'block' (I can't justify this - if you can you should believe this answer much more).
'holds' indicates putting letters inside.
'summer treats' becomes 'ices' (I've seen this in another clue).
'block' going within 'ices' is 'ICE-BLOCKS'.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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