Being a bit of a terror, do wrong (3)
I believe the answer is:
err
'do wrong' is the definition.
(I've seen this before)
'being a bit of a terror' is the wordplay.
'being a bit of' indicates a hidden word (I've seen 'a bit' mean this (the answer is formed by a bit of the clue)).
'ERR' is hidden within 'terror'.
(Other definitions for err that I've seen before include "Be inaccurate" , "Be mistaken" , "Go astray" , "Miscalculate" , "Bungle" .)