Soldier appears leaderless and embattled (6)

I believe the answer is:

sapper

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

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

(Other definitions for sapper that I've seen before include "Military miner" , "Writer" , "Something that wears down" , "Private in the British Royal Engineers" , "Engineer private" .)

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

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