As worn by soldiers with pikes? (5)

I believe the answer is:

kepis

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'as worn by soldiers' is the definition.
Although both the answer and definition are plural nouns, I cannot understand how they can define each other.

'pikes?' is the wordplay.
'pikes' can be anagrammed to 'KEPIS'.
However, I'm not clear how this is indicated.

'with' acts as a link.

Can you help me to learn more?

(Another definition for kepis that I've seen is " French military caps".)

I've seen this clue in the Evening Standard.

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