Account sent back about old soldier (7)

I believe the answer is:

trooper

I'm a little stuck... Click here to teach me more about this clue!

'soldier' is the definition.
(I know that trooper is a type of soldier)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for trooper that I've seen before include "Private soldier" , "He swears" , "Proverbially swearing soldier" , "ship" , "Cavalryman" .)

I've seen this clue in The Times.

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