Not packing anything sleeveless? (7)

I believe the answer is:

unarmed

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

'not packing' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for unarmed that I've seen before include "Type of combat" , "Having no means of defence" , "Like Venus de Milo" , "Defenceless" , "having lost certain members" .)

I've seen this clue in The Times and The Sunday Times.

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