Faux pas made by troublesome children heading off (6)
I believe the answer is:
errors
'faux pas' is the definition.
'troublesome children heading off' is the wordplay.
'troublesome children' becomes 'terrors'.
'heading off' means to remove the first letter.
'terrors' with its first letter taken away is 'ERRORS'.
'made by' acts as a link.
(Other definitions for errors that I've seen before include "Mistakes and omissions" , "Gaffes" , "Blunders, slips" , "boobs" , "Subject of Shakespearean comedy" .)