The most common and most likely answer to this crossword clue is the 7 letter word ARMREST
I've seen this crossword clue in The Times
A
R
M
R
E
S
T
More clues leading to the result ARMREST
- Support for upper body member in seat
- A specialised soldier on the way to give support
- Married wearing collar one’s found on a sofa
- Frenchman in detention requires support on seat
- Around room forcibly assert support for chair
- Frenchman amid apprehension getting physical support?
- Part of sofa in which a jolly group sit
- Ready to explode? Nap in part of chair
- Support for member, male, in nick
- Give weapons to others in support
Buddy explains!

The straight part
We know that "Support for upper body member in seat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case support for upper body member in seat = armrest.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 ARMREST mean?
ARMREST noun- Part of the seat of a chair that is designed to support the arm.