Mistakenly (2,5)
'mistakenly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for in error that I've seen before include "Wrong" , "Mistaken" .)
'mistakenly' is the definition.
(synonyms)
This is all the clue.
(Other definitions for erroneously that I've seen before include "Wrongly" , "In an incorrect manner" , "Mistakenly" , "in a wrongful manner" .)