Piece of toast for military sort (7)

I believe the answer is:

soldier

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

'piece of toast' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for soldier that I've seen before include "Military man" , "Army fighter" , "Member of army" , "One enlisted" , "Member of the armed forces" .)

I've seen this clue in The Sun.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.