Crossword Genius

Avoided invoice? (4)

Ross

I believe the answer is:

duct

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

'invoice?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

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

Can you help me to learn more?

(Other definitions for duct that I've seen before include "Passage for cables etc." , "Pipe, tube" , "The Eve of St - is a narrative poem by Keats" , "Channel" , "Pipe for cables or air" .)

I've seen this clue in the Sydney Morning Herald.
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