The most common and most likely answer to this crossword clue is the 8 letter word ADAPTORS
I've seen this crossword clue in The Daily Telegraph
A
D
A
P
T
O
R
S
Buddy explains!

The straight part
We know that "plug-in devices" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plug-in devices = adaptors.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 ADAPTORS mean?
ADAPTORS noun- One who is capable of adapting to differing situations.
- One who adapts a thing, e.g. a play.
- A device or application used to achieve operative compatibility between devices that otherwise are incompatible.