You're never right in it (5)
I believe the answer is:
error
'it' is the definition.
The definition suggests a singular noun which matches the answer.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for error that I've seen before include "Fallacy, mistake" , "Faulty judgment" , "Bug" , "wrongdoing" , "Boob" .)