Don’t be long invoicing, having quietly inserted flyer (9)

I believe the answer is:

spoonbill

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

'flyer' is the definition.
(spoonbill is a kind of bird)

I can't explain the remainder of the clue.

(Other definitions for spoonbill that I've seen before include "flyer" , "Wader" , "one rarely seen in the UK?" , "Tall wading bird" , "Large wading bird" .)

I've seen this clue in The Times.

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