A lot of fresh confusion after invasion by one deadly opponent (7)

I believe the answer is:

nemesis

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'a lot' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

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

Can you help me to learn more?

(Other definitions for nemesis that I've seen before include "Vengeful justice" , "Nee Miss (anag.)" , "(Fate's) retribution" , "Greek god of vengeance" , "Bane" .)

I've seen this clue in The Times.

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