The most common and most likely answer to this crossword clue is the 7 letter word DEVILRY
I've seen this crossword clue in The Guardian
D
E
V
I
L
R
Y
More clues leading to the result DEVILRY
- Mischief and deadpan gags having malign influence
- Reckless behaviour wrong in prohibitionist
- Charged back into abstemious surroundings to make mischief
- Sympathy for finishers was flipping wickedness
- Mischief in uninspiring witchcraft
- Wickedness of year spent in retirement
- Sin involved in torrid mischief
- Wicked, getting into unproductive mischief
- Bad behaviour arising on stage — tedious to be around that
- Wickedness in tedious mischief
Buddy explains!

The straight part
We know that "Reckless behaviour" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reckless behaviour = devilry.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 DEVILRY mean?
DEVILRY noun- Mischief.
- Wickedness; cruelty.
- An action performed with the help of a devil; witchcraft.
- An act of such mischief, wickedness, cruelty, or witchcraft.