Found out concealing key to correcting erroneous input (4)
I believe the answer is:
undo
'key to correcting erroneous input' is the definition.
(an undo button corrects a computer error)
'found out concealing' is the wordplay.
'concealing' indicates the answer is hidden within the clue.
'UNDO' is hidden within 'found out'.
(Other definitions for undo that I've seen before include "Open buttons or ruin" , "Cause downfall" , "Cancel, annul; open" , "Loosen (knot)" , "Wreck" .)