Some embarrassing transgression? (3)
I believe the answer is:
sin
'transgression?' is the definition.
(I know that sin is a type of transgression)
'some embarrassing' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'SIN' is hidden within 'embarrassing'.
(Other definitions for sin that I've seen before include "Lapse against moral law" , "Transgression of moral law" , "Wicked deed" , "Breach of moral law" , "Serious error" .)