to correct sb's mistake; to make sure that sb knows the correct facts when they have had the wrong idea or impression
PUT / SET SB STRAIGHT (ABOUT / ON STH)
Meaning of PUT / SET SB STRAIGHT (ABOUT / ON STH) in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005