Wrapper girl quietly sent off, containing verse (8)

I believe the answer is:

envelope

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

'wrapper' is the definition.
(I know that envelope is a type of wrapper)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for envelope that I've seen before include "what's to be posted in here?" , "Coat" , "Even pole, strangely, can contain a letter" , "jacket" , "Even Opel has a letter wrapper" .)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app