The most common and most likely answer to this crossword clue is the 7 letter word REMOTES
I've seen this crossword clue in The Daily Telegraph
R
E
M
O
T
E
S
Buddy explains!
The straight part
We know that "Devices for raising volume in endless relaxation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case devices for raising volume in endless relaxation = remotes.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 REMOTES mean?
REMOTES noun- An element of broadcast programming originating away from the station's or show's control room.
- To connect to a computer from a remote location.
- A device used to operate an appliance (such as a television), vehicle or mechanical toy from a short distance away.
- A means of doing something from a distance.