Taking on the enemy (8)

I believe the answer is:

engaging

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'taking on' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for engaging that I've seen before include "holding fast" , "coming together" , "Fighting - winning" , "Winsome" , "embarking on military action" .)

I've seen this clue in The Globe and Mail.

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