Needed for cocktail party in very cold block in the south (3-5)

I believe the answer is:

ice-cubes

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'needed for cocktail party in very' is the definition.
I know nothing about this answer so I can't judge whether this works.

'cold block in the south' is the wordplay.
'cold' becomes 'ice' (I've seen this before).
'block in' becomes 'cube' (synonyms. I am not sure about the 'in' bit.).
'the south' becomes 's' (abbreviation).
'ice'+'cube'+'s'='ICE-CUBES'

Can you help me to learn more?

(Other definitions for ice-cubes that I've seen before include "They cool drinks" , "Accompaniment for drinks" .)

I've seen this clue in The Irish Times.

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