International alliance building legacy of co-operation, initially (4)

I believe the answer is:

bloc

'international alliance' is the definition.
(group of nations, eg the Eastern bloc)

I don't understand how the rest of the clue works.

(Other definitions for bloc that I've seen before include "Allied country group" , "A number of countries" , "Political grouping of countries" , "Group of countries with a shared aim" , "Alliance - coalition" .)

I've seen this clue in The Guardian.

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