Run down section conceals way to rectify input errors (4)
I believe the answer is:
undo
'way to rectify input errors' is the definition.
I can't judge whether this defines the answer.
'run down section conceals' is the wordplay.
'conceals' indicates the answer is hidden within the clue.
'UNDO' is hidden within 'run down section'.
Can you help me to learn more?
(Other definitions for undo that I've seen before include "Ruin or undermine" , "Cause the ruin of, or cancel" , "Loosen; annul" , "Loosen or reverse" , "Remove the wrapping" .)