Soldier without underwear? (8)

I believe the answer is:

commando

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

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

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

Can you help me to learn more?

(Other definitions for commando that I've seen before include "Army unit" , "Amphibious military unit" , "One soldier" , "Kilt-wearer might go" , "Military unit specially trained for raids and assaults" .)

I've seen this clue in The Sun.

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