Mischief-maker's warrior groups (5)

I believe the answer is:

impis

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'warrior groups' is the definition.
The definition suggests a plural noun which matches the answer.

'mischief-maker's' is the wordplay.
'mischief' becomes 'imp' (mischievous creature).
'maker's' becomes 'is' (I am not sure about this - if you are sure you should believe this answer much more).
'imp'+'is'='IMPIS'

Can you help me to learn more?

(Another definition for impis that I've seen is " Native warriors".)

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

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