Like Mars but unlike Venus (5)

I believe the answer is:

armed

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'like mars' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for armed that I've seen before include "Prepared for battle" , "Prepared for attack" , "Bearing weapons" , "Prepared and equipped for a confrontation" , "ready to fight" .)

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

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