English rogue involved in odd mistake (7)
I believe the answer is:
erratum
'mistake' is the definition.
(I know that erratum is a type of mistake)
'english rogue involved in odd' is the wordplay.
'english' becomes 'E' (abbreviation).
'rogue' becomes 'rat' (rat can mean a nasty person).
'involved in' indicates putting letters inside.
'odd' becomes 'rum' (rum can mean strange or dubious).
'rat' inserted into 'rum' is 'rratum'.
'e'+'rratum'='ERRATUM'
(Other definitions for erratum that I've seen before include "Faux pas" , "Mistake (in publishing)" , "Misprint" , "Printing mistake" , "mistake in text" .)