How and when soldiers move? (5)

I believe the answer is:

march

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'move?' is the definition.
(I know that march is a type of advance)

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

(Other definitions for march that I've seen before include "Walk in a resolute manner" , "make progress" , "Walk smartly" , "Military walk; month" , "Parade" .)

I've seen this clue in The Irish Independent.

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