The most common and most likely answer to this crossword clue is the 14 letter word DO-IT-YOURSELF
I've seen this crossword clue in The Guardian
D
O
-
I
T
-
Y
O
U
R
S
E
L
F
More clues leading to the result DO-IT-YOURSELF
Buddy explains!
The straight part
We know that "Unprofessional activities/Unprofessional activities" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unprofessional activities/unprofessional activities = do-it-yourself.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does DO-IT-YOURSELF mean?
DO-IT-YOURSELF adjective- Of or pertaining to do it yourself