Hi mattrom
I have a book called "Chambers XWD - A Dictionary of Crossword Abbreviations".
I shows DE as an abbreviation for "department".
I had a quick search through the normal internet sites and could find no other reference to this abbreviation, but as the book was published by Chambers I assumed that it was kosher.
I am quite happy for you to ignore this clue in your judging if you think that it is "off colour" - I am fairly new to crossword compilation and have much to learn.