Being wrong, by the way, is not harmful (6)
I believe the answer is:
benign
'not harmful' is the definition.
(I've seen this in another clue)
'being wrong by the way' is the wordplay.
'wrong' is an anagram indicator.
'by' means one lot of letters go next to another.
'the way' becomes 'n' (Compass direction - North).
'being' with letters rearranged gives 'benig'.
'benig'+'n'='BENIGN'
'is' is the link.
(Other definitions for benign that I've seen before include "Liberal" , "'Pleasant and kind, not harmful (6)'" , "Kindly; not harmful" , "Favourable" , "Genial; not harmful" .)