Soldier shot back to cover second-in-command (7)

I believe the answer is:

trooper

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'soldier' is the definition.
(trooper is a kind of soldier)

I don't understand the remainder of the clue.

(Other definitions for trooper that I've seen before include "Proverbially swearing soldier" , "Cavalry 21" , "Soldier, proverbial swearer" , "Private soldier" , "ship" .)

I've seen this clue in The Telegraph.

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