Awful Prime Minister is, alas, ultimately missing opposition to growth? (4-11)

I believe the answer is:

anti-imperialism

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'alas ultimately missing opposition to growth?' is the definition.
I know nothing about this answer so I can't judge whether this works.

'awful prime minister is' is the wordplay.
I cannot really see how this works, but
an anagram of 'prime' is 'imper' which is within the answer.
'is' could be 'ii' (more than one I) and 'ii' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

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I've seen this clue in The Guardian.

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