The most common and most likely answer to this crossword clue is the 7 letter word BEDREST
B
E
D
R
E
S
T
Buddy explains!
The straight part
We know that "support for sitter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case support for sitter = bedrest.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 BEDREST mean?
BEDREST noun- A device used to support a person sitting up in bed.
- Confinement to bed, often under instructions of a physician, in order to recover from an injury, an illness, or the frailty associated with other physical discomforts such as a difficult pregnancy.