Avoided invoice? (4)
I believe the answer is:
duct
'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" .)