The most common and most likely answer to this crossword clue is the 4 letter word PLOY
I've seen this crossword clue in The Times
P
L
O
Y
Buddy explains!

The straight part
We know that "device" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case device = ploy.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 PLOY mean?
PLOY noun- A tactic, strategy, or gimmick.
- Sport; frolic.
- Employment.
- To form a column from a line of troops on some designated subdivision.