Incorrectly do right about turn (3)
I believe the answer is:
err
'incorrectly do' is the definition.
(to err is to make an error)
'right about turn' is the wordplay.
'right' becomes 'r' (common abbreviation).
'about' becomes 're' (regarding).
'turn' says the letters should be written in reverse.
'r'+'re'='rre'
'rre' in reverse letter order is 'ERR'.
(Other definitions for err that I've seen before include "Be inaccurate" , "Bungle" , "Miss the mark" , "do something you shouldn't" , "Deviate" .)